This appears to be the smallest of the P.u.W. bombs. These came about as the result of a collaboration between the Prfanstalt und Werft evaluatuion centre and Goerz of Berlin. The bombs were trialed in 1915 and started to see service in 1916. As stated by Bonnex they were avaialable in a variety of sizes 12.5, 50, 100, 300 & 1000kg. The smallest differed from the rest in being thick walled and was thus a fragmentation bomb. Certainly for the Germans maybe the Allies as well, these bombs were quite a technological leap. Prior to this the Germans had been using Karbonit bombs, they have the appearance of Disney cartoon bombs and normally the pilot or observer picked one up, lent over the side of fuselage and let go of it. From an aiming point of view it was very hit and miss (pun x 2, not intended). The adoption of the PuW bombs allowed them to be mounted horizontally on the fuselage. The bombs were fitted with a fuze that had a delay option and incorporated centrifugal arming. The latter was a bit of a mixed blessing, as if the aeroplane crash landed the crew were afforded a bit of protection. However, to ensure the bomb spun on release the Germans were reluctant to put mounting lugs etc., on the body, thus the bomb was suspended in a cradle by two steel cables (one front and rear).
Regards
TimG.