I hate to say it but "excellent condition" and "working perfectly" are subjective ratings. Anyone who's selling something will often have the opinion that their gear is better than new.
Things like hopup rubbers or magazine lips are consumables. That pistol could have been running just fine the last time used, but then it could have been put away for months or years even prior to the sale.
Step one is pull out that rubber and post up a really clear macro photo in the Dr's orner. Ask for folks with Sys7 or NS2 pistols to compare to theirs. You may strike it really lucky and find someone near you with one to compare hands on.
Airsoft, where nothing is hurt but feelings.