James,
You can know this with the serial number and listing you can get on :
Leica Screw Mount Serial #'s Sorted by Number
ex :
1953 IIIf ELC 684001 685000 1000
1954 IIIf with delay mechanism 685001 699999 14999
1954 IIIf with delay mechanism ELC 710001 711000 1000
1954 IIf 711001 713000 2000
1954 IIIf with delay mechanism 713001 729000 16000
1954 IIIf with delay mechanism ELC 729001 730000 1000
1955 If 760001 762000 2000
1955 IIf 762001 765000 3000
1955 IIIf with delay mechanism 765001 775000 10000
1955 IIIf ELC 773001 774000 1000
saw that you did not miss the golden summar !
Regards
JC