Gaku Ichibu Die Study
In mid-2024, I began an in-depth die study of Keicho ichibu in hopes of understanding them better. Along the way, I decided to add Gaku ichibu to the mix to look for any crossover in dies. They were the same size, weight, and have the same design on side A (with Mitsutsugu's signature), so it seemed quite possible that a transitional die pairing could exist. As it turns out, it does - and we'll talk about it shortly - but I also ended up with information useful for authenticating Gaku ichibu and other interesting data. This page will discuss the main conclusions drawn from the die study, and the buttons below will take you to pages detailing all individual dies for each side with statistics and key diagnostics.
Since there's currently no universal agreement on which side is the obverse, I've opted to dub the side featuring Mitsutsugu's signature as "A," and the side with the denomination as "B."
The Keicho ichibu die study is still underway and will be released as a research paper in both English and Japanese when complete (planned by the end of 2025). While I only have photos of 32 Gaku ichibu to study, I have close to 300 Keicho ichibu - a much more time-consuming task. In the meantime, I hope you'll enjoy this detailed look at Gaku ichibu.
Full Die Map
Each line on the die map below represents one example. All Gaku ichibu that I've been able to find photos of are represented on this map as of April 2025.
Overall, this is a very simple and tidy die map. The most noteworthy general takeaway (in my opinion) is the repetition of almost every die. In all 32 coins, I've seen only one die that isn't found on multiple pieces - Gaku-B1. Every other die is found on at least two coins. This implies to me that this sample represents most, if not all, possible dies.
Use in Counterfeit Detection
I would be highly skeptical of any Gaku ichibu that doesn't use a die included here. While it's certainly possible that other dies are out there, without multiple examples or crossover with an already known die, I would proceed with caution.
In fact, this study has omitted one example that was sold as genuine but that I believe to be counterfeit. It has fully unique dies on both sides, no incuse kirimon stamp, and the inner dot border on side B is very sloppy compared to genuine pieces. Any of these features alone would raise a red flag, and together they were enough for me to completely eliminate it from the study. I encourage serious scrutiny if you own or are considering buying a piece that doesn't match any of the pictured dies.
Keicho Transitional Die Pair
The most common Gaku A die can also be found paired with a Keicho B die. If you note the diagnostics described for Gaku-A8, you can see that both coins below clearly use the same die.
I found the Keicho ichibu below through its PCGS cert number, and unfortunately the only image available is of the full slab. I've enlarged and cropped it so only the coin is shown, but it's not the clearest photo. It's also worth pointing out that this Keicho ichibu was clearly struck over what was originally a Gaku ichibu; if you look at the left and right borders of side B, you can see where the previous three-layer Gaku border was struck. I've seen a fair number of Keicho ichibu struck over Gaku ichibu, but both sides are always fully restruck using Keicho dies. This is the only example where a Gaku side A is paired with a Keicho side B, and I have to assume that both sides were restruck together.
What does this tell us?
In the past, it was believed that Gaku ichibu were minted in Kyoto, while the first Keicho ichibu were minted in Edo. If this were the case, it may not make sense to group Gaku ichibu with the national issues of the rest of the gold ichibu series. However, while most modern Japanese sources state that it has now been traced to Edo, they rarely discuss how this is known. The presence of Mitsutsugu's signature provides substantial evidence (discussed in "Solving the Mysteries of the Gaku Ichibu"), but this die pairing is further proof. I haven't seen any suggestion that the earliest Keicho ichibu were minted anywhere but Edo. Pairing an early Keicho B die with the Gaku A die places the Gaku dies in Edo.
In addition, it further supports including the Gaku ichibu with the rest of the series. While it was originally minted as a regional coin and a prototype for a future national coinage, the fact that it was minted in the same location and with some of the same dies as the first official national coinage makes it clear that it should be included in a discussion of the rest of the series.
Incuse Kirimon Stamp Observations
Each Gaku ichibu technically involves three dies: A, B, and the kirimon stamp. The kirimon stamp is so small with so few details that a thorough die study isn't possible with the quality of photos available for most pieces. However, thanks to a few damaged stamps, I am able to make a few observations.
Both examples of A4/B4 use a kirimon stamp with a clear die crack running through it, confirming that both examples share all three dies. I haven't seen this cracked kirimon die on any other examples. (See Gaku-A4 for more commentary.)
In addition, of the ten A8/B8 examples, nine share the same kirimon stamp with a large die break (circled on the first image below). This stamp later developed a second die break on the opposite side. One example may use the same stamp before the break occurred or be a different stamp altogether. (See Gaku-B8 for more commentary.)
These are the only kirimon stamp dies I've been able to confidently identify, suggesting that they may generally line up with the A and B dies.
While more data is needed to draw a confident conclusion, this does have some implications regarding the minting process. As I understand it currently, each coin was struck by a mint worker (or possibly Goto Mitsutsugu himself) with the A and B dies, then verified personally by Goto Mitsutsugu (or a singular representative) and stamped with the kirimon if approved, meaning only one kirimon stamp was in use at a time.
If only one die pair was in use at a time (ie. only one person was striking coins at any given moment), it makes sense that these pairings would more or less match up. It's reasonable that all the dies would fail/be replaced at a similar time, resulting in a majority of pieces where all three dies match across examples. However, if multiple die pairs were in use simultaneously (ie. multiple people were striking coins at once), we should see a lot less consistency with the kirimon stamp within dies.
Since the only traceable kirimon stamps are consistent within A/B die pairs, it suggests that only one person was striking coins at a time. More study is needed and this should be regarded as a loose theory, but it's interesting nonetheless.
As far as positioning, the stamp is most often seen on side A (26 examples) and occasionally on side B (6 examples). Five of these six examples are on Gaku-B7 and Gaku-B8, which I'm relatively confident were among the last Gaku ichibu struck, suggesting they may have become less consistent in placement as minting progressed.
Wide vs. Narrow Calligraphy
A 2022 Japanese auction listing for a Gaku ichibu included the following in the description (translated):
"Gaku ichibu coins are roughly divided into small and large characters, with the larger characters predominating. In 2014, one exemplary small character and one exemplary large character were offered for auction (lot no. 341 small character, lot no. 342 large character), so please take a look."
Lot 341 from the auction referenced is Gaku-A1, and lot 342 is Gaku-A7. I haven't seen this distinction made anywhere else, so it may be fairly new within the Japanese collecting community. Based on a general look at the dies, I believe it's possible that "small characters" refers only to Gaku-A1. I invite you to look through the A dies with this in mind and consider where you would draw the distinction. If you have any insight on what the general consensus is within Japan, I'd love to hear from you.
Finding More Examples
I've been scouring the internet for photos of Gaku ichibu since 2020. While I believe the current study includes the vast majority of pieces that have been imaged online, I invite photos of any other examples. Specifically, if you've purchased a piece in a private sale or acquired it prior to 2010, it's likely missing from the study and I'd love to see photos. Populations won't be updated here very often, but I will add any new dies or significant die pairings as they appear or are shared with me.
All photos used in this die study are shared for educational purposes only. No coins or photographs are owned by the author. Photos come from PCGS, Ginza Coin, Taisei Auctions, Nihon Auctions, Auction-World, Stack's Bowers Galleries, and Japan Antique Coin.
The Rectangle Coins