Hi,
I just bought a Vivitar 24mm 2.8, the serial number is 91103xxxx, so if
this is correct, it was build in 1991 by Cosina.
It's appearance doesn't match any of the 28s in the bestiary, it does however share the filter thread diameter and the rubber grip on the focus ring with the A22.
Otherwise it resembles the A21 (Cosina!), though I haven't seen the other of the "Two variants with different markings on aperture ring. PK-A/R mount."
It came with the original (unopened!) packaging and paperwork, here are the specs:
Filter thread: 52mm
Min. focus distance: 19cm (1:5 Makro)
19cm to infinity: ca. 165°
Opt. construction: 7 lenses in 7 groups, 5 aperture blades
Coating: "Multicoated"
Mount: PK-A/R
Dimensions(ØxL): 61x40mm
Lens:
Contents of the original packaging:
I have posted a set of test shots with the DA 18-55 WR for comparison at dslr-forum.de (it's in german but I think you'll get the gist):
www.dslr-forum.de/showthread.php?t=1127442
I don't know how it compares with other Vivitar 24s or the K/A/FA*24 but it certainly wipes the floor with the DA 18-55 WR.
It's well worth the 40€ ($50) + shipping I paid for it, anyway...
I've seen several versions of Vivitar 24s so far (including quite a few in this thread), so to me it seems like a good idea to make a bestiary for the 24s as well...
If wants to do that, he/she can use my shots (including those in the Thread at dslr-forum.de) or ask me for the originals / better ones.
Jan