I found this vintage AMCAM 28mm, f2.8, multi-coated lens SN 102900 in a thrift store in Santa Fe, New Mexico on vacation for $25. I used a Nikon-to-NX adapter by K&F Concept to mount to my Samsung NX1.
I could find nothing on the Internet about this lens, so I assume it is a 'branded' lens manufactured by a Japanese company. I compared this lens with other vintage of 28mm focal length and the closest I can find in build/looks was a 28mm, f2.8 from Cosina . Probably manufactured in the very early 80's.
Note: This 28mm lens has an equivalent of a 42mm focal length equivalent on the NX1's APSC crop sensor.
All photographs in this post are 'as-photographed' with all camera filters and picture effects turned off, with the exception of any black and white photo, where the camera was set to 'Monochrome'.
Conclusion after taking these initial photos: This is a sharp lens that produces crisp photos in bright light, nicely saturated colors and warm textures. I really like this 28mm lens.
Downtown Phoenix neighborhood home f11, 160-sec, ISO100, EV0