This is what I found out this far:

Weapon was proofed in Germany 7/1928

(The date of proofing is stamped in being 7/28)

The discription of the round being 8,8 MM for a 9,3 mm round is typicall for later in the 1905-39 period)

The weapon was proofed in Ulm or Suhl pre 1954 (the eagle proofing, (cant determine which eagle it is exactly)

It has a pre 39 german proof for an expres rifle barrel (The E)

It has a pre 39 German proof for inspection in a finished state (the U)


Hope you can tell me even more of it.