In 1990, base metal coins in circulation included (potentially)...
Canada: 1920 1c, 1922 5c
Germany: 1949/50 minors
Netherlands: 1948 1c,5c,10c,25c
Switzerland: 1800s
UK: 1947 1s,2s (as 5p and 10p until small coins introduced)
US: 1800s
Not a lot, eh? (I'm sure I missed some...)
I've yet to come across anything before 1917 (wheat) personally.