country.sys: EUR currency support
country.sys has support for giving the currency for a given country / codepage combination. It currently does not contain support for EUR.
My proposal is to implement EUR as a currency for codepage 858 #39 and cp 437. The FreeDOS country.sys also implements this for codepage 850. But I do not think that it is wise to do it, for the sake of compatibility. If one really wants EUR, she/he can set CP 858, and instead leave 850 in the historic currencies.
Maybe a definition HISTORIC should be used to stick to historic currencies etc. when compiling COUNTRY.SYS, but otherwise use current currencies.
Tangentially relevant: Staging has both historic and modern set of settings - see https://github.com/dosbox-staging/dosbox-staging/issues/3128 and linked PR, etc.
A lot of COUNTRY-relevant info there.