b) U shape or round base with aluminum knobs, eye pieces & focus exactly 10x and 20x superior quality with aluminum fitting. 

c) College pattern cast iron heavy round base with brass pipe and focus is exactly 10x and 20x superior quality with brass fittings.

d) Rust proof rack and pinion with special guide inside on heavy triangular cast iron base. Complete with 10x and 20x eye piece and reflector with beautiful storing cabinet.