Help with a Nero please?

[Hullblazer]

My father has extended his watch collecting to military timepieces and this is one of his recent purchases, a Lemania Nero.

It is obviously a timing device of some sort but is numbered 1 through 0 and has a sub-dial able to track up to 10 revolutions.

He thinks it's either a bomb-aimer's piece, from the RAF, or it's a torpedo timer from the Navy.  Which war, we're at a loss for.

Hand scratched on its reverse is "WA 15111".

I can find little on it, can anyone on here give this piece some history?

[wls1971]

You need to do a search for a Type A-8 ground speed navigation timer, The sweep seconds hand should should take 10 seconds to do a complete turn how it was used I dont know but will have a look in my military watch refrence books.