My first post, but thought I might actually be able to help some.;)
ETKA, the VAG parts catalog, lists the 5N as being used in the 5000 from 1/83 to 7/84. AAZ in the 5000 from 10/86 to 5/88. No listing for the 3U in the US ETKA so it's probably a European model.
HTH
Dan