relic,
A Rock 6,076,xxx One of 28,500 made in that 3rd Block.... Wonder how many are left
If I remember correctly from what I read in War Baby..... Rock Ola used only Flip sights in the 1st block: 1,6-1,7.
In the 2nd: 4,5-4,6.... 3rd block: 6,07-6,09..... and 4th (last) block: 6,1-6,2.... All can be found with the Type II Milled or Type III Stamped Adj rear sights. Note that the use of Type 1 Flip sights were also used by Rock Ola in these 3 blocks also.
Again from memory most often spotted has been the H in the shield and I.R. CO
Inspecting the Dovetails may give you the clues you need to how it left the factory.
Look at the staking or lack of it. If a adjustable was original, it will probably have just punch marks in the appropriate areas with no stake slashes nearby.