You have a nice little display there.
The motor is worth about $60-80 on average. The fact that you have the original box, papers and even two non working Nicad’s collectors may be interested in it and ‘may’ be willing to pay a little bit more for it. I say this because the old Nicads may or may not attract collectors. I never heard of anyone collecting old Nicads but as a box set it may seem attractive to some..
I bought a pair of used Astroflight 25’s a couple of years ago for $120 which was a fair price for them which brought them to $60 each.
The motors are difficult to find and someone is going to want it. The fact that you have a NOS (New old Stock) motor will likely get the attention of some collectors. I would use the fact that the motor is (NOS) as selling points to drive up the bidding.
If I was going to sell a similar motor I would set an ebay reserve for $60 and let the market determine the final price.
If you had the second motor and sell the complete set there would likely be a bidding Frenzy because collectors will jump on the opportunity to get the entire original box set.
On another forum I am on we do “ebay” alerts. This is when something unique that is RC boat related is found on e-bay and if the finder does not want to bid on it they post the link as a courtesy to fellow boaters and the community will be tipped off about out the item. This brings attention to the item and brings more interested parties to the table.
If you do post it on e-bay, let me know and I will add it as an e-bay alert to get it some attention.