I know nothing about these. This is a first for me but I saw these and remembered seeing people talking about similar coins so I picked them up. What should I know about them? The bigger one was labeled 4 mon and the others 1 mon. Smaller ones said 1739 and 1737.
Based on what I know they were still cast at this time, not struck like the similar bronze coins of the 1800s. Your second pic is upside down i can take a look for more info in a minute.
I recall seeing somewhere that the ‘wave pattern’ (on the first one) indicated one of the oldest Japanese coins (maybe 17th century). the reason there is a square hole is because these were cast, not struck (emulating Chinese coins), and so remnants of the sprue was left on the coin. The coins would be mounted on a square shaft to hold them in place to file off remnants of the sprue. The hole had the added benefit of being able to string coins together to ease larger purchases.
It's all in the book "Early Japanese Coins" by Hartill. I have a copy and I'll see what I can find. There are so many variations on these coin types that exact matches could be challenging, but here's what my mind came up with based on matching pictures. The first one seems to match a Shin Kanei 4 Mon (四文), catalog number 4.252, dates 1768 - 1769. All are listed as "Very Common." JNDA 133.75. The second one, which someone already said was upside-down, resembles a Shin Kanei dated anywhere from 1739 - 1745, listed as "Common." The third one looks like a good match for Shin Kanei Koume-Mura, Musashi province, catalog 4.155 or 4.156 (probably 4.156, since the other one has a small hook on the leftmost line), given the character on the back. Dates 1737 - 1742. All listed as "Common." JNDA 131.30 or 31. Someone may have already mentioned that all of these old "cash coin" style coins were cast, not struck. The book mentioned has an entire section on the manufacturing process, which is pretty fascinating. The coins emerged from their casts on large "trees" from which they were cut into individual coins and polished. The Meiji Restoration of 1868 inaugurated the era of struck silver coins in Japan.
