The age of the machine is irrelevant unless it is of course NIB.
You can still describe a 35 year old machine as honestly and accurately as 5 year old machine. As long as you are familiar with the older machines, then you are in a position to sell them. Most dealers are in "unfamiliar territory" with EMs, and I quote from a dealer (not an AP Sponsor) - "EMs are too hard to fix and you cannot get parts for them anymore". That's because the Dealer has no experience in preparing and selling EMs. If a dealer sells an EM - it is usually as a "project" - as they don't know if it is complete.
Same can be said selling a DMD. If you don't know the product then you need to ask others. This applies for a private sale or a dealer. Ask any dealer or importer about the process of preparing a machine for resale into the home market. There is a process that is very simple - "as is" - straight off the container - all bets are off - what you see is what you get. Reconditioned or restored - pay big $$ but have a look at each coil sleeve. They will be replaced. It is the "somewhere inbetween" that catches most. This is where you need to look at the machine, play the machine, look under the playfield and adjust the pricing accordingly in the spirit of the sale. I've never heard of "partial refunds" or "freebies" post sales. This should never happen if the two parties agree.
Bottom line - regardless of age, make or color - go and see the machine. This eliminates all doubt. Not all sales go to plan, but there are ways to make it an enjoyable process !
