Original etchings and old silkscreen prints produced by hand have created the idea that some work ie. low numbers in the edition are more valuable
This is due to the printing process where the plates are inked, and it is suggested that earlier numbers could be slightly clearer than the later ones.
Some sales people can unwittingly confuse a client by implying one number of a photo litho is better or more valuable than another
This is completely incorrect.
If you wish to keep the original framing on a signed print, it is purely a matter of preference,
and has absolutely nothing to do with preserving the work or keeping it in its original state so it is more valuable.
On the contrary, framing in the 1960s and 1970s was by today's standards, rather poor.
Today we use mainly museum glass, which not only looks invisible from most angles, but more importantly, protectsthe work from ultra violet light and stops the irreversible process of it fading.