During the 1960s Canon's 50mm Macro was a simple four lens Tessar construction, probably with less-than-ideal performance. Minolta, in 1963, had introduced its 50mm 1:3.5 Macro Rokkor which was a sophisticated 6-lens Planar using high refractive Lanthan glass. Pentax had a slow 4/50mm with radiactive Thorium glass, and Nikon's 3.5/55mm Macro was derived from early processing lenses for chip manufacturing.

And Topcon? Their Macro lens had a lightly longer focal length and only five lenses (the f=58mm focal length usually permits to omit one lens, compared to a f=50mm construction). The RE Macro Auto Topcor 58mm 1:3.5 is well built, it can be focused down to 1:2, and it has a fully automatic diaphragm and light meter coupling - which means that exposure can be measured through the lens and with open aperture. While today this is absolutely normal today, it was not at all in 1963, when Topcon introduced the Topcon RE SLR.

		TOPCON AUTO-TOPCOR RE 58mm 1:3.5 Macro                  (5 Linsen / 4 Glieder)