I'd be very surprised indeed to find a fine sporting Ross .280 M-10 stamped up with any sort of stamps at all, nevermind fourteen of them! OTOH, if you could possibly be referring to a/some Military MkIII Ross rifles, that's a different story. Ross model identification is not really all that difficult, and a quick check over at RossRifle.com should clear up the confusion.
If possible, are you in a position first to really identify just which Ross we're discussing here, then supply a detailed photo of the actual "PLY" stamps? Once we're all on the same page, please tell us if some/any of these rifles show additional Brit Proofmarks on barrels and receivers.
Anxiously awaiting your response(s).....