Do you know this Stirling model?

[carlossp]

I've received as a Christmas gift an antique Stirling Cycle-Type engine.
Almost identical to the one pictured in page 49 of Andy Ross book Stirling Cycle Engines.
The engine is in full working condition - we have tested it today - and we are very curious
to know about its origine and manufacturer.
It belonged to a great grand father of mine and has stamped on it the initials: D.R.G.M
folowed by the number 288423. Both the initial and number are below another stamped
number 14.
One of the grase nipples of the main piston has the word "PETROLEUM"
We beleave that D.R.G.M means "Reichgebrauchsmuster"

If any of you has a clue about the origin of this machine, it will be of grate help.

Thanks
Carlos