I've seen a couple of people ask similar questions recently, as to what versions of the Sony Playstation 3 are "backward compatible" and which are not.
I found this guide (courtesy of the ubiquitous Wikipedia) which may help:
(Edit: I tried to cut/paste or recreate a table, but I couldn't do it on this forum, so here's a link
PlayStation 3 - Wikipedia, the free encyclopedia
If you want to know what model numbers to look for in your region, use this:
Also, I found this handy quick-ref Venn diagram:
Hope this helps.
(Maybe a Mod can sticky this for future ref?)