OK, so I have obtained a Hasselblad 503cx (from 1989) equipped with an A12 back (from 1970) and a Carl Zeiss Planar T* 100mm f/3.5 from 1981. According to a data sheet I have downloaded from zeiss.com/photo, it has a "bayonet for Hasselblad Series 50". The lens' outer diameter by the bayonet is about 58-59mm (I'm a couple of thousand kilometres away from my calipers, so this measurement is eyeballed...). The lens' serial number is 6362xxx. Do I have the correct datasheet? If not, where can I find exact information? What I'm after is an adapter ring that lets me use my existing filters. Who makes it? Thanks in advance!