These coins, minted in nickel and copper-nickel, come from the old Republic of China, before the People's Republic (communist China) took over in 1949. That is Lin Sen, Chairman of the National Government, on the front, and an old Chinese spade coin on the back.
5 FEN: 17 mm diameter
10 FEN: 21 mm
20 FEN: 24 mm
50 FEN: 28 mm
See this page [Click Here] for related coins without Lin Sen.
As modern coins made of non-precious metal, just about all of these coins carry very low value. Even fully uncirculated, the values are decent, but not through-the-roof, as follows:
ALL DENOMINATIONS, COMMON DATE, 5, 10, 20 AND 50 FEN:
worn: less than $1 US dollar approximate catalog value
average circulated: $2
well preserved: $10
fully uncirculated: $20
There are, however, some better dates in the series. To find them, you first have to figure out how to read the dates. For Westerners, this can be difficult. Dates are expressed as years elapsed from a base date. In our example below, year 25 is 1936AD, and year 31 is 1942.
Here are what the Standard Catalog lists as better dates. Values after the dates are for coins in well preserved condition. Coins with more wear are worth much less.
5 FEN YEAR 28: $35
5 FEN YEAR 25 WITH CHARACTERS (e.g., p'ing) AT PORTRAIT: $120
10 FEN YEAR 25 NON-MAGNETIC: $45
10 FEN YEAR 31: $120
50 FEN YEAR 32: $45