Quote Originally Posted by rwanttaja View Post
This has some similarities to a Battenberg Course Indicator:

http://en.wikipedia.org/wiki/Battenb...urse_indicator

Other options include an artillery or torpedo plotter. It has some similarities to a pelorus, too, but it doesn't have the sighting notches.
Ran the trapline with a Fly Baby friend who's retired from the RCN. He ran it through HIS trapline, and this came back:

It's likely a Battenberg relative velocity calculator or a knock off by a Commonwealth country. I was still using them for Fleet manoeuvres in 1994 with the Australians.

Of course, a relative velocity calculator can be used for many other things than Fleet Manoeuvring. Torpedo firing solutions (which is, after all, a rel-vel calculation between the torpedo and target), relative wind calculations, etc.

There is usually a third arm which may be missing in this example.

I'd be interested in it if the other Ron doesn't scarf it up.

Ron Wanttaja