Hasselblad 503CW dust marks on negatives.
After getting repeated dust marks on my negatives, I tracked the culprit down to the secondary shutter blind covering, breaking down. Itís a fleck of a sort and is kind of delaminating due to age. Rubbed a Q tip on them and it was just coming off so easily and was getting on the film during expos
Not got time to go into research but the stuff is not needed. So I used cotton buds and some camp stove fuel and got the fleck and glue off very easily. Looks like a new 500CM now in the back.
So if anyone has the same issue, itís an easy inexpensive fix.