I mentioned my old telescope's secondary mirror in this answer (stiffness) but I'm not certain I am remembering correctly. My first telescope was a Edmund Scientific 4¼ inch Newtonian reflector. This was in the 1970's. I seem to remember that the secondary mirror was a right angle prism rather than an elliptical front-surface mirror.
Am I dreaming or mis-remembering, or did Edmund use prisms on at least some 4¼ inch Newtonians?
Either way, any discussion on the tradeoffs between front-surface elliptical mirrors and 90° prism secondaries would be appreciated.
Source: John M. Pierce's HobbyGraph Articles HobbyGraph #15; Diagonals and Diagonal Supports.