Probably not the question you thought I'd ask. I've had one before, and just traded for one again.
The last one I had was marked on the block "3/4" - this one is marked "4/2"

What do these numbers mean? Do they come in different lengths?

Someone here probably has figured this out. I didn't measure the last stock, so have no comparison. This is the Romanian sidefolder stock, works with the standard single tang stamped receiver, similar to the DDR and (Egyptian) stock.

The Romanian wire folder? Mine doesnt have a mark.