If the C of A and Annual was anticipated by up to 62 days and say for example the annual was completed on the 1st of Jan but the C Of A expiry was Mar 1st, then the CAA will issue a New Certificate dated from Mar 1st and NOT Jan 1st, the old one will remain in force till Mar 1st at which point you should return the expired cert and run on the new C of A cert from there on..... this would then throw the annual out from the C of A, but you would normally realign the annual and C of A at the next C of A..
so you could have a case of the C of A appearing to have been issued after a 50 hr as you are only seeing the later cert, though the C of A was indeed carried out with the annual......
This could be done again I suppose if the Annual and C of A was anticipated again with the C of A being carried out again early.
Also with the C of A going over to the EASA version and being done yearly they are now all over the shop......
Ask your maintenance company, they should be able to contact his company and clear it all up....