It seems to me that there was no such thing as a 'standard' Burns model back then!
Every one I've ever seen is slightly different in some feature or other! Bit different today with CNC production consistency and quality control I s'pose!
(I ashamedly admit that I used my Burns Vibra Artist at high volume, playing material by Cream, Hendrix, The Who and The Byrds - which was the 'in' stuff in 1967 at the time I owned it... )