Careful guys. Of the bases shown in JC Harrisons book(s) I believe only his Type II ("REDFIELD" in block letters on the right rear quarter) was used on original rifles. The Harrison Type 1 Mount (Unmarked) is a korean War vintage replacement part which is occasionally seen on rebuilds.
The other mounts shown in Harrison are commercial mounts and I have seen no evidence of military use in A4 production.
The mount photographed in TM 9-270 (and reused in TM 9-1270) does not appear to have the beveled section at the rear of the base. All i can say is that except for the manuals I have never seen that type of mount on a legitimate A4. IMO the reason for the bevel is to provide finger clearance for adjusting the eyepiece when the Lyman Alaskan (M73). Possibly an early A4 with the commercial style mount was sent to Raritan Arsenal Publications Department to be photographed for the manual??
One final point while I am on a roll. I doubt very much that the unmarked mounts seen in Lyman packaging were actually manufactured by Lyman. It just doesn't make any sense that they would tool up to make a product that they never made commercially and did not hold the patents on - especially for a rinky dink spare parts order. I a much more likely scenario is Lyman received an order for scopes, bases and rings and simply farmed out the mounts to Redfield. Its a classic "make or buy" scenario from Business Administration 101.
I know some authorities have stated in print that Lyman made the mounts. However, the same folks have gone on to say they have no information as to the total quantity made. This suggests to me that they are not working from documents or contracts but are probably just looking at a package which is stamped "Lyman".
Regards,
Jim