Mauser Parabellum: Internal Numbering

[mauro]

Hi Tom,
Today I had the opportunity to see the Navy commemorative number 73. Actually this pistol has the number 073 internally engraved in the rear toggle link.
The same collector has an early production (1972) in 9mm. This pistol has the last three digits of the serial number engraved in the BreechBlock.

In addition this guy ordered a pistol to Mauser in 9mm with, in addition, a barrel with receiver in 7.65mm.
What is interesting is that this set barrel and related receiver is numbered E13.005352. The second part of the serial number follows the normal pattern. The first part no. Do you have any idea about the meaning of this E13. I assume that only the complete guns was numbered with 10. or 11.
Any idea?

The current owner is a very important Belgian shooter, he has an unbelivable set of customized sights and toggle for shooting purposes.
A pleasure for the eyes!

I really hope to be able to buy some items. I cross my fingers!!

Ciao
Mauro