MIDO Identification

Hey all, i found this vintage Mido Multifort Superautomatic with Calibre 916P that has a caseback #646380. It seems that the caseback and calibre may be older than the dial indicates. The dial says Mido Mutifort Superautomatic and then down above the sub-second, it says power wind. it seems that the case and movement may be from the 40's, but the power-wind language didnt come into use into the 50's. Any thoughts are helpful.