Tamron Adapt-A-Matic 300mm F/5.6 Model 670Au: This lens was available in three versions. Production obviously started sometime before 1972 as indicated on Tamron's web site. We are not sure if the 670Au model name applies to all three versions. Initially there was the first model which featured a metal knurled focus ring. Then there was a subsequent model which featured a rubber focus ring yet still did not have slots on the aperture ring for the aperture coupling band included with later versions of some Adapt-A-Matic mounts. The final version of this lens featured a rubber focus ring plus the slots for aperture coupling bands.

Lens Specifications:

Lens Model	670Au
Focal Length	300mm
Aperture Range	f/5.6 — 22
Angle of View	8°
Optical Construction (Groups / Elements)	2 / 4
Min. Focus from Film Plane	98" (2.5m)
Macro Mag. Ratio	—
Filter Size	62mm (front)
Diameter	2.8" (70mm)
Length at [w/Nikon mount]	[8.0" (203mm)]
Weight	28.0 oz. (795g)
Lens Hood	Built-in
Accessory	—