Retouching with ZIG pens

I'm currently in the process of printing from old negatives, some of which are 25 + years old and perhaps not surprisingly a fair proportion of these negatives are scratched or have spots in them. I'm currently using some SpotOne that I have and need to replace soon.

But that got me thinking is there anything else in the market and what did I used to do. Originally I trained at Art College (Fine Art) a large proportion of what we did was printing and photography and then I worked as a printer for a number of 8 years or so predominantly in silkscreen and in both we used to use Zig Opaque pens to spot in and repair negatives (amongst a variety of older and more dubious methods). When in college we also used these pens for the same purposes in photography.

I just found one of these old pens, and wondered whether anyone else had come across them or use them, and if not what do you use?

If you can't find Spotone, look for Dr. P. H. Martin's dyes. They seem to work well. I've used opaque pens in graphic arts, but would never try them in analog photography.