Conservation framing and 'museum' UV blocking glass was rarely in the 1960's and '70's
Prints were often attached to the mount with sellotape (not acid free tape used frequently today)
The print may be stuck onto board using glue and a heat press
Its life from publication to the present day is the most important factor of any print
If it has survived the last 50 years and is in good condition with strong original vibrant colours
then it will probably be fine for the next 50 years, as long as it is kept away from strong sunlight and damp
Normal 2mm. picture glass cuts down UV by 50%, so with double glazing it is generally quite safe
UV blocking museum glass can be expensive, but if you wish to be 100% sure it is a good option
Museum glass cuts most of the UV and has non-reflective properties too
This gives a superb effect, but comes at a cost.
Museum glass for a good sized picture could be £200-300
The number of prints in the edition, does have a certain bearing on value
But this has to be weighed against the subject matter which is always more important.
'The Cart' 850 edition will always be more valuable and sought after than 'The Lowrys' 300 edition for example