Very similar to the Air Arms Zeroing target.. Although theirs was a smaller and a simpler version with a spinner instead of a ringer to confirm zero. I've been trying to get hold of one for a while but they stopped making them ages ago. I can't even find an old secondhand one.
I asked AA about them at this years shooting show. They said they stopped making them due to low demand and they no future plans to reintroduce them
Are you looking to produce them in any quantity?
I'd be interested.