Hi Alan
If you go to
http://www.gunson.co.uk you will find links to a lot of their products. Each product has a pdf file attached to it which is the instruction manual. I had a quick look but cannot fond a "Tachostrobe" listed. If you don't find it on their site, give them an email and I am sure they will have the one you want archived. Over many years I have always found the guys at Gunson really helpful.
Cheers
Gary
Eeyore rides again !!
EOR14W - Persian Aqua 2L Dhc, Now rebuilt and looking lovely - Sprint engine being prepared!