While browsing the forum today I saw a few posts that peaked my interest. Someone claimed that the ST61 was ONLY made as a w/c gun! Totally wrong, or as Dick Wray used to say - as wrong as communism!
ST61 was commercial nomenclature for the MG15 used by Rheinmetall. It is mentioned in Musgraves excellent book German Machine guns. A friend of mine in the UK was one of the buyers of surplus MG15's from Romania and he had hundreds of guns in a basement in Kent where we picked our way through them. They were mostly ST61's but also many MG15's mixed in. It is my recollection that the black tool/parts wallets came from the same source. I regret not getting an ST61 marked gun at that time, but anyway, these were all air cooled guns. This was around 1996 or so and the water cooled MG15 had not turned up on the market in any numbers yet.
The water cooled guns have never been documented by anything other than hearsay that I know of. No official pictures or documentation other than the sheet from inside the crates. The guns are converted air cooled guns and the conversion, although marked as French, look very eastern bloc to me and to most others that have taken their time to examine them.
Whoever converted the guns, it is very doubtful that it was something done by the German ww2 regime. It would be interesting to establish contact with Romanian collectors and see what they have to say about the water cooled MG15 - if anything at all. Do we have any Romanian members that can chime in?