Can anyone advise on the following signage fitted in a cockpit above the Blind Flying Panel.

This aircraft must not be flown at speeds greater than 350 KNTS IAS
The landing gear and the flaps must not be extended at speeds greater than 35 KNTS IAS
Nor must this speed be exceeded when landing gear and flaps down

The Blind Flying Panel has a No Smoking sign also fitted

From what I can make out of the image no gunsight of any type appears to be fitted to what looks to be a well worn cockpit with nothing else of note. I may be wrong with the air speeds but I think they are right. Any ideas most welcome to try and identify the period of this one.
Thank you....