Unidentified Japanase/Chinese Cash Coins?

Neither coin is Japanese.

The top one is from emperor Ch'eng Tsu (1368-1398) of the Ming dynasty.
The writing on the coin is a Hung Wu T'ung Pao (contemporary Japanese imitations exists but yours is not one).

The second coin is from the Manchu emperor K'ang Hsi (1661-1722) - obverse needs to be turned 90 degrees clockwise.
The reverse (which is upside down) shows that it is from the mint of public works.

Have a decent collection of Chinese, Vietnamese, Korean and Japanese cash coins.
The Ming dynasty ones are quite easy to determine (at least for me) by the style of the characters, so I quickly opened my album with the cash coins to see which one it is. Btw, I have also a Japanese imitation of it.

Almost all of the Manchu dynasty coins can be easily identified as such by the reverse, which indicates the mint. The emperors title on those is always top to bottom and once one is used to the characters one can quickly check which one it is.
If you have the 1601-1700 Krause catalogue you should find your second coin in there, for the Ming dynasty one you need other catalogues.

If you consider me to be fast with those coins, you have seen nothing yet - the resident expert here is 'manymore', he can identify them while sleepwalking.

In my issue of Krause 1601-1700, the number is 356 with Sch.#1451 as note.
The 'Sch' refers to the catalogue by Schjoeth. Your Ming coin is Schjoeth#1166 (and Mitchiner#3641+ from another catalogue).

If you look at these. They probably the same time? And the second one is used as bouton? Because the rare reverse...?

I'll hold off on the ID's of your last two coins, but to answer your question: yes, these coins were made in crazy amounts. The one-cash coins (tong bao) were worth a face value of 1/1000 of a silver tael, which was about 35-40 grams of silver. I am not sure of each individual coin's buying power in terms of everyday commerce, but they were quite frequently strung together into a "string" of 1,000 coins to make them easier to transport. In terms of US currency, the busing power would have been about 0.15-0.2 cents on the old silver standard, or about 1.4 cents at today's silver price.

These coins were heavily produced during the time of the Western middle ages, but saw production on a new scale thanks to trade with Spain. Spanish silver mines in the New World coughed up silver by the boatfull, and quite a bit of it ended up in China to be traded for silk and other luxuries. Especially during the reign of the Kangxi emperor (1621-1722) the national treasury's funds rose from 15 million tael to just under 50 million by 1702. It's believed that during the most prosperous years, billion of cash were minted to keep up with the influx of silver and demand for luxury goods. That would explain why the Kang Xi Tong Bao cash are still worth only a dollar or two, 300 years later.

Finn: Why hold off on the identifications? The attributions are correct. As to your comment, the uptick in silver importation only affected the silver to copper rate in China, but was one of many factors in the 18th century affecting relative values of the two metals in China. The most prolific coin production was during the N. Sung and Qing dynasties and is generally regarded as an indicator of increased trade and commerce during periods of relative stability in the region as a whole.

Vince, I don't understand your question. All cash coins were cast until 1883 when the mint in Guangzhou opened and milled (sloegmunten) 1 and 10 cash coins were produced in brass, and even until about 1914 small amounts of cast coinage were still produced. Just because the reverse is blank doesn't make it old, it's just blank. you have to identify them off of the obverse inscription and sometimes some marks on the reverse.