[schwarze-man]

Hi, The caps that I have, show a few interesting details. The DBU marked Kraftstoff caps come in vented and unvented type. The casting has the same part number 8-4520A cast into the reverse of the small attachment screw arm, despite the fact that the casting is different in detail, particularly the "air vented" cast lettering on the vented type. They are made from an Electron magnesium. It can be deduced that the vented caps were generally fitted on unpressurised fuel tanks, also generally gravity or low pressure refuelled. It is not known to me if there were specific aircraft with internal tanks that required unvented Kraftstoff caps. The common external 300 Litre droptank required air pressurisation to transfer the fuel up into the aircraft system and so, they had a sealed cap. You can see that in the photos of the droptanks in post#6. There is another point, the DBU caps have a large screw arm for a 12mm threaded stud and a small screw arm for an 8mm stud. This arrangement controlled the fitment of the cap to one orientation. You can see this on the second photo in #6 which I think shows the early standard of droptank cap with the sealed type 8-4520A DBU cap. However, later droptanks had a standardised sealed cap, that I think is shown in the first photo of #6. The standardised late cap has both arms with cutouts for 8mm studs. The late cap is made of alluminium alloy and has no words cast into it. In original condition they are painted a light green/blue. The standardised droptank cap has the following id cast into the metal of the arms: 3355.4 gyq N.9 (where 3355.4 is the alloy spec and gyq the manufacturer code) on one arm and, R-05615-39 (the part number) on the other arm. Cheers

SM