to correct myself somewhat, these small labels were also common for various other "clubs/organizations/societies". In Yugoslavia, there is a great series of these for the National Mountaineering Society. I don't have any, but they are on my radar.
I just recently bought one similar to this (mine is a 10 dinar piece). This is for the National Front (Communist party membership) in Zagreb. There are similar pieces for the national level of the NF.

The following is definitely for a trade union membership booklet. there are at least 8 different values for these, plus some un-valued ones that are series issues (III, IV, V, VI, etc). there is even one without value or series, marked as "bolestan" which I gather was for disabled/invalid members.
