I'm no real expert but having had 6 of these rifles it sounds like it's a newer type, with the safety going through the action, the earlier ones never did that. You'll probably find a HW77/97 or 80 safety will fit your 35 if you were looking for a replacement.

also the 11mm dovetail would make me come to the same conclusion.
The fact it has no serial number could suggest the barrel has been changed over the life of the rifle???

Age wise...... probably a late 80's or 90's rifle?? another thing to help date is the style of the stock? does it have a rounded bottom to the pistol grip area? is it flat bottomed or does it have a black cap fitted?

HTH PAUL