[spangy]

As ithacaartist has pointed out only the "Gesichert" was factory filled.
Other members here have called all other 'white' fills as putting 'lipstick on a pig' and in that regard I agree.

If you must use a white filler for whatever reason the cheapest and easiest to remove later on when you have regained your senses is 'white out' typewriter correction fluid.

To each his own but if Luger manufactures thought that white filled proofs would be a good idea they would have 'made it so'. JMHO