Interesting, a TR block with a King Carol Crest. King Michael crests are known in the SR and TR blocks. It looks like the changeover to King Michael crests was not clear cut. Not surprising, since ZB was trying to crank out VZ24 rifles as quickly as possible at the time.
Late 1940 or early 1941. King Michael replaced King Carol on September 6, 1940. King Michael crested rifles are known in the SR and TR blocks. These rifles would have been made after that date. It looks like the bulk of the AR-YR rifles (if not all) were made in 1940.