Original 66 value ?

[MDriskill]

A big deal with those Diana Giss-system double-piston guns is of course the condition of the seals. That one sounds to be in good shooting condition, which adds a lot of value compared to one that needs a rebuild.

The 66 was typically furnished with the older Diopter 60 rear sight. The matte green finish is correct for late examples of this unit, where older ones were a glossier black or charcoal gray. This coordinates with the heavy barrel sleeve on the gun, which has a similar matte phosphated finish.

For what it's worth...here in the US a good-condition 66 with working seals and original barrel sleeve and sights would easily be a $450 rifle; more if in exceptional condition or having well-figured wood.