While on the subject of PP scopes, I've had one for a number of years and have finally decided to have it mounted on a period-correct SMLE. The leather case was marked to rifle J2015 but then re-stamped to rifle P8498. The scope itself is in very good condition and complete with the end caps - it also came with a base which I assume is a reproduction but looks excellent.
Does anyone know what size of screw would be correct to fasten the base to the receiver?

Also, I have a 5-power Fidgelands scope that is faintly broad-arrow marked on the ocular end.
I do have the Skennertonicon book, but would like to find out how these were mounted if anyone has any information?