Looks to be an early example....if contemporary, the spindle mounts are pre '53 or thereabouts, the grease nipples stick out to catch your leg. Later models, '53 onwards the grease nipples point rearwards, as in your lower picture.
Forging number on the frame member is the same for left and right sides, one on hand appears to be marked 67-4118 BSA, (yeah, or some boss eyed similar combination) through the paint and grime. Find this on the left hand side of the forging, looking from the rear, below the large hole for the footrest mount. Like yours, mine measures 12" between pinch bolt centres. My frame also has a brazed on side stand lug, so is a later variant, post '53 or thereabouts.
'49-'53 Plunger parts book for A7/A10 lists three variations for the frame rear section pre '51 (67-4070), pre 53 (67-4102), then onward, 67-4094
The plunger design was also introduced on other models, so in all probability the same basic forging appears on B and M Frames.
Swarfy