Terry Parker – 10th April 2023 at 20:42 

E10 appears to be ‘looking’ down rather than “on top”.

My periscope is looking down too. Oh yes, strange thing… But it was first thing, that gave me an idea, that this periscope is from aircraft.

This is a minus of Internet communication, that you will never understand how we communicate, in what tone and mood. I beg your pardon, in no case did I want to hint that there is something bad in our communication, I correctly understood the question. Thank you very much for your help! I already wrote to them. But here’s what’s interesting .. I wrote in groups on Facebook, where there are former pilots from these aircraft. And they say they have never seen such devices on board. The task becomes even more difficult and even more interesting. I will wait for answers from other museums.

Hello everyone!

I just received reply from National Museums Scotland.

Just want to share it with you. Next steps I need to visit or contact to museums which have Hawker Siddeley Nimrod on exhibition. 

Here is the answer:

“I must confess I’ve not seen one of these before and thus it is difficult to be certain about its history and use. However, I can tell you that the second part of the serial number in image indicates that it dates from 1972. Going by what is stamped on the side of the wooden crate, this appears to be an On-Top Drift Sight. These seem to have been used, but only very rarely, on Hawker Siddeley Nimrod maritime patrol aircraft and I can only assume it was used for long-range navigation, presumably over open seas, to measure drift due to wind and thereby allow for adjustments to course.”

So, it is really interesting case for me. And I hope, for you too.