It wont be a collection. Its a genuine pocket spill. Chinese coins were in circulation continuously until the 1630`s, this includes all those old coins, all mixed together. About mid 1630, they became non-legal tender. There were a variety of different coins available in Japan before the 1600`s. Some Japanese made, some Chinese and some from Annan (Vietnam). Even within the Japanese coins from this period there was a considerable variety of styles; Shichusen, bitasen, clan coins and trade coins. All of them were given the officail denomination of one mon, regardless. In reality it could often be somewhat different, with vendors refusing to accept coins that were unpopular or copies (shichusen). Chinese coins were dominant and higher quality, but they were used for centuries, literally. One chinese coin could be in circulation for 400 years.
The importation of Chinese coinage to Japan by the governments at the time started from the 12th century.
Nice find. And its good to see some other relic hunters in Japan having some success. If you`re in Kyoto, near old temples, even the trails will have a protection order, so don`t be too obvious