So I found a small group of old Japanese yen that I've obtained from various places- the 3 100 yen coins came from the 5 for $1 bin at a local coin shop. My question is, (since I don't really collect Yen; I mostly focus on British coinage) are there any key dates here, or can I give them to a friend so he can spend it?
These look to be Showa 44, 52 and 56. You can add to 1925 to get the Western dates: 1969, 1977 and 1981. My 1995 Krause guide doesn't show any dates carrying a premium after the Cu-Ni series started in Showa 42 (1967). Before that they are 60% silver and carry a metal premium. Back then the metal value was well below face value, but it's much higher now. At 5 for a dollar you can't go wrong with a coin that's worth $0.96 face if you have a way to spend them. If I ever go back to Japan I'll probably stuff my pockets with small change to repatriate! The 100 yen bill is pretty cool. Those have been obsolete for a while. I don't know that they carry much of a premium. Technically the Series B notes are still legal tender, but one would probably get strange looks if one tried to spend one, kind of like a $2 bill in the US. I doubt cash registers have a slot for them any more.
Oh, and the top middle 10 yen is the reeded type (Showa 26-33) That one looks to be Showa 29 (1954). Those carry a slight premium in lightly circulated condition, maybe about 15 cents value. I pick the older reeded ones up whenever I see them in a 10 cent junk bin. Best not to get me started talking about Japanese coins of I'll talk your ear off! Left: Smooth edge, Right: Reeded edge from the 1950s.
All of the coins shown above still circulate in Japan today (even the reeded varieties can show up, though they are less common), so they basically have face value, especially considering their condition. Also, those series don't really have any major key dates unless they're in absolutely pristine or proof condition. The 5 Yen coin (五円), the one with the hole, from (if I'm seeing that date correctly, the picture is a little dark on that coin) 昭和四十八年 or 1973, is a "Gothic Lettered" variety, the variety that currently circulates. Earlier types of this coin, from 1949 - 1958 are called "Kaisho Lettered" and, like the reeded 10 Yen coins, have a slight premium, but nothing to get too excited about, unless you have a very shiny 昭和二十七年 example. The 100 Yen (百円) banknote is a series B from 1953 (昭和28年) and, in its condition, probably has a value somewhere between $3.00 - $7.00. That type does have 2 varieties, though, the first having more value than the second. It's hard to tell which is pictured based on the photograph. If it is the first type, it could be worth anywhere from $15 - $30. The reverse should depict the Japanese Diet building. I don't think that it currently circulates, not that 100 Yen would buy much anyway, being worth roughly $1.00 US. The coins look to add up to 365 Yen, so they are collectively worth about $3.51 US. Keep the bill, spend the coins.
