Omega Supreme has become one of the most popular (and valuable) vintage G1 toy around. He was, however, very delicate, and as a result, many surviving Omega Supremes have some battle damage. Here is a comprehensive list of questions to consider asking sellers (or checking on your Omega Supreme if you are a seller):
1) Electronics: Omega Supreme should walk in robot mode and roll in tank mode (with rotating turret). Additionally, his 'eyes' should blink on and off during operation. Make sure the electronics work. If the seller says he does not have any batteries, ask seller to check for any corrosion around the battery contacts. Omega Supreme can lose as much as 50% of his value if the electronics don't work.
2) Legs: Omega Supreme's legs (treads in tank mode) had a rather peculiar transformation, because of which, many an impatient child ended up breaking the fragile walk mechanism. The walk mechanism involves a spring-loaded pin that, if damaged, will not allow the leg to move in robot mode. This is the gimpy leg syndrome. Have the seller check that Omega walks steadily on BOTH legs--make sure neither leg is gimpy. Again, if the seller says he does not have any batteries, ask the seller to carefully examine the leg/tread area, specifically the inside area. If the treads are pulled out, and Omega held parallel to the floor, the legs should stay out straight, and not flop down. There are tabs on the outside of each leg/tread the seller should PUSH in to correctly return the legs back into position for vehicle mode. If the seller has any trouble doing so, there may be a problem with the walk mechanism.
3) The yellow shields/leg clips: There are a total of six, with two of each of three different sizes--large clips which attach to the front of the legs, and medium and small clips which attach to the back of the legs. Make sure all six are included as replacements are about $10 a pop!
4) Tracks A-H: These parts are relatively cheap, but often aggrevating. They are often damaged, but most sellers won't know it or recognize it. For Tracks A-D, have the seller check the upper areas, where these parts clip to the robot's hips, make sure there is nothing broken or chipped. For Tracks E-H, make sure the bottom section (the end where the letter is) has the small clip that connects to the foot-if broken, the foot will be very loose.
5) Backpack: Make sure the small grey clasp on back is unbroken, and the two yellow 'hangars' are unbroken.
6) The claw arm: Make sure the orange 'claws' when fully extended, stay firmly in place and do not easily fold back down.
7) The turret: Make sure the turret (red cannon on the head) is unbroken, this is a very fragile area. If you are shipping or receiving Omega Supreme, make sure this area is well protected for shipping!
Of course, there can be other flaws, but experience tells that if an Omega Supreme passes all of the above tests, he should be a keeper. Good luck!