The red T* is on the barrel, not benzole sorry bout'that.,ser# is Nr 2595460 on barrel and 1302 1307 U on inside of lens by lens mount.
Mike
That would be a lens from 1971.
A 'strange' one, from one of the 'strange' serial number ranges (the one starting with 259).
This number range was used (among other things) for lenses sold to behind the Iron Curtain, where Zeiss could not use the Zeiss name, or any of the Zeiss lens names (They used the brand name OPTON instead, calling a Planar "Pl", a Sonnar "So", etc.).
Richard Nordin lists one black Opton So f/5.6 250 mm C lens, with serial number 2594384, i.e. earlier than your chrome lens (which does not necessarily mean it was made earlier too). It has T* coating.
The number range was apparently also used for 'special' lenses. Like ones to be used in publicity shots, in catalogues.
And for prototypes.
With T* coating beginning to be introduced in Zeiss/Hasselblad lenses a coule of years later than your 1971 lens, it may well be that your chrome T* 250 mm Sonnar is a 'prototype', a lens used to test the effect of T* coating. To see whether it would be worth the bother.
That could also explain perhaps why it was stamped in february, and then again in july: a normal production run lens (completed in february 1971), pulled from stock, given T* coating and a new serial number (and a mark on the barrel) 5 months later.
Could be something else completely too.