I'm not quite sure what you have.  If it is a Caltar HR 300/5.6
it probably has not had a previous life.  It was probably sold
as new by Calumet.

There is an interesting article by Kerry Thalmann (May/June
2003, in View Camera) which lists the repertoire as he
knows it of Caltar HR lenses (in table 11 on p. 40).  A 300
mm. is not mentioned.

It is interesting that depending on the focal length, they
seem to have been produced by several sources and with
different performance.  The longer focal length lenses seem
to be in the range of 60 degr. coverage.  The possibility
it is really a re-labeled 300 mm. Grandagon seems a
unlikely.  I think those are at least rare and am not aware
that one was ever made.

Still, to put another interpretation on "previous life" it is
likely that it was made on contract to Calumet by
someone else (since that is how Calumet often did
things).

As you know, Calumet is a retailer who uses the Caltar brand for
merchandise manufactured for them by an OEM.  Over the years, Caltar lenses
have had a reputation for decent quality at slightly less exhorbitant
prices than those of the OEMs who actually made them.  For example, modern
Caltar II-N lenses are every bit as good as the prime-labeled Rodenstocks,
and in fact they come in a Rodenstock box.

I am looking at Kerry's VC article - he lists several 300mm f5.6 lenses:
       Type S (1970-75) by Rodenstock
       Type S-II (1976-83) by Schneider
       Pro (second series) (1982) by Schneider
       Type II-N (1984-present) by Rodenstock

but he does not show that there was a 300mm lens in the "HR" series.  These
lenses were manufactured either by Topcon or Rodenstock (depending on FL)
in 1984.

There was also a 300mm f6.3 lens in the first Pro series (1980)
manufactured by Komura.

So the bottom line is that the lens that you are considering appears to be
paradoxical.  Are you sure about the HR designation?

Could you post an image of it somewhere ? Or at least a few more
details such as filter size and perhaps even the country of origin ?

==
    John S. Douglas
    Photographer & Webmaster
    www.legacy-photo,com
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