Diff identification

Hi all, I've just replaced what I think was an automatic rear diff with the correct manual diff ( previous owner garage fitted wrong diff which made the 4wd wind up ) anyways I now have a diff that I think is an automatic ratio diff but I've only got the po word for it . I want to sell the diff as it's perfectly serviceable and was nice and quiet however I was wondering if there is a way to confirm that it was definitely an automatic diff and not a manual from a different year for example . Is there a way to do this ?? Stamped numbers perhaps ? Any ideas please

Count the teeth on the crown wheel and the pinion. Divide the larger by the smaller. If auto this should be 4.090

Sorted , 4.090 it is 45 and 11 thanks for that , by the way the manual one you sent me was spot on Thankyou