as I understand it there are steel ones and alloy ones, so a magnet is the obvious way to tell them apart if that's the only difference
the best thing to do for checking part numbers is to get VIDA installed on one of your PC's (
https://docs.google.com/document/d/e...i3cpHBdsZa/pub ignore all the stuff about the nano just start halfway down. enter your VIN and it gives you a full parts catalouge and diagrams. later you can get a nano if you want, stick it on a laptop and use it for diagnostics as well
the slightly easier option would be to have a look on scandix
https://www.skandix.de/en/spare-parts/1/ and you can get part numbers from there to seach ebay and other places
there is also the powerflex option where you retrofit polybushes, firmer and possibly also should last longer.
https://www.volvoforums.org.uk/showthread.php?t=330523"
https://www.volvoforums.org.uk/showthread.php?t=315538