Hi Roger,
Pretty sure they are going to be homemade and typical of some home made scopes of the period. The quality of course depends on the skill of the constructors.
My Next door neighbour (Dr Ed Kruzins) and I built one similar to the scope on the Ivory Alt Az mount around 1972. Mount was quite similar and the tube we built was square with an aluminium frame with thin plywood sheeting at the top and bottom for baffling. Mirror cell was made of plywood. That was an 8"/F10 scope. Ed ground the mirror with a kit from Astro Optical to better than 1/8th wave. Optically the scope performed really well, but an 8"/F10 Newtonian is pretty unwieldy by todays standards and you weren't taking it anywhere in a hurry.
That scope was stage 2 of our astronomy careers. I pursued a career in business and finance and continued as an amateur astronomer. Ed on the other hand pursued a professional career in astronomy and space exploration and is now the Director of the CDSCC In Canberra controlled by the CSIRO and NASA, which follows an illustrious career in Satellite and Defence technology
https://people.csiro.au/K/E/Ed-Kruzins
Cheers
John B
