The User's Review: Elicar V-HQ Macro MC 90 mm f/2.5 Macro Lens

I believe, this lens is one of the best macro lenses for manual focus, because of its 1:1 magnification scale, f2.5 maximum aperture, and smaller size. My copy has a KA mount, meaning that I can set aperture size on Pentax DSLR camers when using the A gear on the aperture ring on this lens (it has the A position, but no A-lock commonly seen on Pentax KA lenses).

The User's Review: Two 55mm F2.8 1:1 Macro Lenses,Branded By Panagor and Vivitar

Probably manufactured in the same factory in Japan, these two lenses are almost identical, except the engraved marks on the surfaces of the lenses.

The Panagor has the magnification scale on the rear side of focus ring, while the Vivitar put the scale on its barrel. On the Panagor, it marks PMC (Panagor's Multi-Coated?). The coating colors, green on front element and yellow on rear glass, are lighter on the Panagor. I am not sure, this is because of the PMC or different aging processes between the two lenses.

The Panagor lens shown here has a MD mount while the Vivitar lens owns a M/SR mount and a screw on its aperture ring (in the last image below). A small metal 'leg' might be mounted at the screw site to convert the Vivitar into a MD mount.

The User's Review: Two 500mm F8 Mirror Lenses,Branded By Kalimar and Vivitar

Both are made in Korea (South Korea, officially the Republic of Korea) , are of MC/multi-coated, have 72 mm-front-filter and 30.5 mm-rear-filter threads, and are mounted on a T-mount adapter that is available for various camera mounts.

The obvious differences between the two are: the surface textures of rubber coats on focus rings, and marks on the lens bodies.

I believe, that they are produced by the same manufacture and their parts are exchangeable. 

The User's Review: Nikon AF Micro Nikkor 60mm 2.8 vs. 60mm 2.8 D

These lenses have been produced for many years and the D lens is still in production. The only difference in their appearances is that the D lens is marked a "D". However, the D lens can pass the distance information to cameras and is very useful when a compatible flash is used.

BTW, in Nikon's English, 'micro' means 'macro'.