The u serial# suffix is indicative of this gun being what is called a 1929 Commercial, manufactured as production transferred from BKIW (DWM) to Mauser. There is an ongoing debate as to whether these were newly-manufactured at DWM or assembled from parts stock by Mauser.
One would expect this gun to have crown/N commercial proofs on the left receiver and under the barrel, and be .30 cal., the largest caliber permitted to the commercial market by the provisions of the Treaty of Versailles.
However, the right receiver eagle (on the left) and the one on the barrel indicate that this gun was reworked by Simson (probably removing the commercial proof). As there seems to be no witness mark on the barrel, my guess is that this Luger has been rebarrelled in 9mm for police or military use.
The Eagle/WaA33is the acceptance stamp of the WaffenAmt, or Weapons Office, indicating that this Luger was modified and accepted for Police or Army use. The mark at the front of the receiver is indistinguishable.
It is hard to tell from the small picture of the left side of the gun, but it looks like it has a sear safety and the left grip is relieved for a magazine safety. These are characterisitc of Lugers in Police service. The 335 you report stamped into the "butt of the gun" could be part of a Police unit mark, but this would be preceded by letters. Nothing can be determined about them as reported.
The right-hand magazine is as one would expect for a Police magazine. These are numbered 1 and 2 (and 3, if there is a third magazine issued with the gun). The Eagle proof is characteristic of late-30s proofing, although there is usually a letter stamped along with this eagle.
The left-hand magazine is a complete mystery. The numbers and Roman-numeral II are quie out of the ordinary, as is the mark below.
The holster is in the Police style, and if it is indeed marked to the gun it is a valuable addition. Even though the flap is detched and the closure strap is broken away, the leather appears to be in good shape and the holster can be restored.