if you go over webster's book closely you will discover his info in the book is not quite right.he is giving you a little info from different purchases and concluding,wrongly,that it gives a complete picture of the scope purchases.
even he wrote that there were 1500 scopes bought in 2 batches.
the first batch of scopes,of 1500, from his date of late 1923 early 1924 would be constructed differently from the scopes in the 28,000,29,000,30,000 serial range.they would have been in the 6,000 to 9,000 serial range.it also looks like there were other purchases of scopes in the mid 1930s.if you go over other parts of the book on the purchasing comisson in the 1920s you will see that they were very low on funds to pay for contracted rifles.they even sold off rifles since they were unable to pay for them.i think the first purchase of scope in the early 1920s were later sold off when the conversion rifles did not arrive.it took 3 or 4 years to arrive.later scopes would have then been purchased after the rifles arrived at NEDINSCO in the late 1920s.
i am currently restoring an argentine Zeiss scope with an argentine number in the mid 1400 range.