HP-35 Serial Number Question

[Corvallis Bill]

I get it now...

The 1143A held on from the first production release design into 1972 and only changed to 1230A when there was the next design change and also released in 1972.

So the calculator I have with the 1143A 41k I can understand why it was manufactured mid-1973, as Dieter states but does still retain those first production run characteristics.

Since my unit has the raised 5 key can I presume it has some historic value in the evolution, compared to the more common 1230A..??

Thanks Guys...!