Yes its the barrel end of an MG151\20 in the blast tube of a DB605. Good sleuthing.
The most important part is you can clearly see the Stützstern or "supporting star" bolt on washer that keeps the barrel centered in the 65mm blast tube. Early blast tubes were 57mm and the washers were pressure fit. This is why in our game's convergence application, the ability to adjust the range of the HUB mounted 109 canons is a gamey reality allowing up tilting of the gun barrel. Same for the yaks 20\37mm and P39. La's were installed level and the round had a 6cm drop at 200m.
With HUB mounted cannon and the mounting in the La, if you wanted to adjust for a range. It was done by adjusting the gunsight so the center of the reticle corresponded to the IP point at your chosen range. The 109 IP for 20mm was set for 700m while for the 30mm was set to 400m. Yak and La were set to 200m. The best I can tell with the P39, the 37mm IP was set for 2000ft by adjusting the gunsight to the 37mm IP point at 2000ft. While the 30cal and 50cal being set to intersect and converge the gunsight sight line at 900-1000ft.