I've compared the early sandcast steering heads to the later sand cast heads as well as post-7414 frames and there are differences, but i cannot remember them, there is a difference in the divots and recesses as i recall.
I have not had the good fortune to have these different types of bare frames all lined up in a row to be able to go back and forth to make first hand comparison observations.
If Chris Rushton sees this post, i am sure he will know steering head differences, he pretty much has a memory like a steel trap.
Just looking at the picture you provided, KP, i cannot say what specific differences there are between early, middle and late steering heads, but obviously you have a picture of an early LH horn mount steering head with the steering damper gussets and like i noted in my most recent post, there are LH horn mount frames without this steering damper gusseting.
I do know these early and later frames have differences in their steering head's gussets, divots and recesses.
As far as other frame differences, I do know and I will say the gussets on the rear section of the frame for the posts of the upper shock mounts, this gusseting is shorter on the sandcast frames than on vin frames somewhere after 7414. Also, the weld beads are not as heavy nor as smooth as later frames.
And I will say the welded seams of early sandcast frames on the two stamped halves of the rear frame to engine mounts (in the swing arm area) are not as tall as later sandcast frames.
The swedged/spot welded sections of the frame where the front down tubes fit into the steering head are less finished, more pronounced, than later sandcast frames.
Overall, the welds on the early sandcast frames are not as clean as welds on later sandcast frames.
I have never had the opportunity of having these different bare frames sitting side by side to account for the differences, this is the only way one could be sure of the differences is to have the frames sitting side by side for comparison.
Seems there are 3 different types of sandcast frames.
1. Early LH horn mount with steering damper gussets.
2. Later LH horn mount *without* steering damper gussets.
3. RH horn mount w/o steering head gussets.