BS-0 semi-universal rotary and dividing head
Manuals:
https://thaler.si/uploads/Brown-and-Sharpe-dividing-head-instructions.pdf
https://thaler.si/uploads/BS-0-manual.pdf
I honestly think, that this is simply one of the most beautiful pieces of engineering I have ever seen.
Not just that it looks great, it also allows you to do things with your drilling or milling machine, that you couldn't do before you had it.
The best offer I could find: https://www.alibaba.com/product-detail/BS-Series-of-Universal-Precision-Milling_60766960546.html?spm=a2700.icbuShop.89.14.19f06cf773Hvgg
Examples:
Direct indexing: 1:51
Indirect indexing (dividing a whole circle): 2:57
Indirect indexing (measuring an angle): 5:11
Music: Vincent Rubinetti, Grant's Etude