British drift sight?

Over on the WIX forum, Taigh Ramey has asked the question.

A gentleman sent me these photos of a device he has had for some time. He would like to know what it is.

It looks like a drift sight to me that is missing the base and/or recorder.

The serial number looks like classic Air Ministry to me with a 1940 date at the end.

Do you have any idea exactly what it might be? Inquiring minds want to know…

http://warbirdinformationexchange.org/phpBB2/viewtopic.php?t=27773

I thought this is a cert for our boffins here! Anyone not able to post directly at WIX can post here (anyway, obviously) and I’m happy to relay.

Regards,