As of the writing of this page (February 2022), I'm still in the process of researching Keicho ichibu. They are, for lack of a better term, a complete mess. PCGS identifies three different types, but there are actually four major types, with three minor variations within those. No English sources do a good job of identifying these types or explaining how to tell them apart. I haven't finished researching the history behind these pieces, but this page will at least show how to tell the difference between the pieces. If you actually have a Keicho ichibu that you're trying to attribute, I recommend taking a look at Shotoku Ichibu as well to be sure it's not one of those.
The Four Major Types
We'll start with the four important and widely accepted types that actually influence value. The graphic below shows one of each, and then we'll discuss the differences.
All photos by PCGS. None of these pieces are owned by the author.
1. Old Keicho Ichibu
It's believed that these may be among the earlier examples struck. They are identified by two features, both on the reverse. The character "ichi" (一), meaning "one," on the right side of the reverse does not touch the dotted border. If you compare the examples above, you'll notice that it goes through the border on all other types.
The other distinction is within the dotted border itself. At the top, there will be four or more dots in each corner, sometimes even a full line of dots across the top of the coin as on the example shown. All other types should have three dots in both upper corners.
I have seen a few occasions where one of these conditions is met but not the other, and it's unclear what that means about the coin in question. It should also be noted that Hartill mistakenly states the exact opposite (shown below); that an 一 character penetrating the border signifies an Old Keicho ichibu. All Japanese sources and dealers agree that this is incorrect. These are the second most valuable type of Keicho ichibu today.
Early Japanese Coins by David Hartill, page 113.
2. Standard Keicho Ichibu
These are the pieces that don't meet the criteria for any other type. They're the most easily confused with #1 and share a PCGS number with them. They're also the most common type of Keicho ichibu and the least expensive.
3. Katamoto (片本) Keicho Ichibu
These have never been given a widely accepted English name that I can find. English references tend to use the Japanese kanji, 片本, instead of assigning a name, although The Standard Catalog of Japanese Coins calls them "One Hon." For now, we'll use the phonetic translation (AKA romaji) of that phrase, which is "Katamoto." 片 (kata-) means one or single, and 本 (-moto) refers to the character on the coin.
On the top right corner of the obverse, there is a character. This character is 本 in a stylized version of grass script (see image below #4). It comes from 本直し, meaning "repair." These pieces were created when Old or Standard Keicho ichibu came back to the mint broken, damaged, or severely worn. They were then remade with this character added to indicate that it was a repaired piece. Today, these are worth more than #2, but average slightly less than #1.
4. Ryohon (両本) Keicho Ichibu
Similar to #3, this one hasn't received a widely accepted English name. Unfortunately, 本 has a different sound in this context, making the romaji names a bit less clear. Regardless, 両 (ryo-) means both, and 本 (-hon in this context) still refers to the same character.
These pieces have the same stylized 本 character as #3, but it's in both upper obverse corners. I haven't been able to determine what the significance is of the different number of repair marks. It may be unknown. These are the most valuable type of Keicho ichibu.
Early Japanese Coins by David Hartill, page iii.
All types are seen with rampant chopmarks, merchant stamps, etc., and finding a truly nice example is difficult. The pieces shown in the first image are far better than average and all straight-graded at PCGS (including the top-pop MS66 Standard Keicho ichibu).
I would also like to point out that there is a lot of variety within all of these types. It's easy to look at the four examples shown and pick out other distinctions, but I assure you, very little is consistent. The differences I've noted are what should be used to attribute them. They are also very often seen with the incuse kirimon stamp found on Gaku ichibu; it just happened that the examples chosen don't have it.
The Three Minor Types
Keicho ichibu were minted in at least three places: Edo, Kyoto, and Suruga. Historically, collectors have distinguished between the mints based on three calligraphy styles, but this has generally fallen out of favor as there's little evidence to back them up. As a result, I would not consider these necessary for a "complete" collection, but in the interest of being thorough, we'll take a look at them. They are mentioned in Hartill, surprisingly, though presented as though equally important for attributing types as the presence of repair marks.
All three styles are defined by the calligraphy style of the top character of the obverse. (I recommend taking a look at The Gold Obverse Design to familiarize yourself with this area. The "top three strokes" are shown there in red, and the "upper character" is composed of the red, orange, yellow, and green strokes.)
All photos by Japanese dealers. None of these pieces are owned by the author.
1. Edo Style
The three top strokes are entirely separate from the rest of the character and are very straight. Note how short and curved the others are by comparison, making this style the easiest to identify.
2. Kyoto Style
The top three strokes are short and lightly curved, though sometimes the far right one seems to blend into the next stroke of the character (orange on The Gold Obverse Design). The defining feature of this style is that the rest of the upper character is narrow; note how much space is left between it and the dot borders
3. Suruga Style
The top three strokes are similar to the Kyoto style, though the far right one always blends into the next stroke. It's differentiated by the width of the upper character; it extends very close to the dot borders. Still, Suruga and Kyoto style are easily confused, and many pieces seem to ride a line between the two.