Guys like me who collect these would really like that earlier serial number. As they are rarer.
What I would do personally is I would buy this one, and then buy another one that is 8X and swap the parts and then sell the other one converted to 12X.
With this early serial converted to 8X again.
Even with the 12X, I think it would sell for $3000-3500. That is just the scope by itself. I rarely see a can sell for less than a thousand. I've seen them sell for as much as $1500 for a nice one.
I think $4000 as a package deal would be fair to both of you. I would personally think anything $3500 or less with the can would be a really good deal in your favor.
I have no real doubt the scope by itself would sell for at least $3500 on ebay and probably would sell for more. The can would probably bring 1200- 1500. But then you loose 13% or whatever with the fees.
For me and my buddies with real rifles, we see that early serial number and it becomes very desirable for us. All evidence is that the early serials were the ones actually sent to the Pacific and many do not exist anymore. The early serial numbers are rare and most serials you see are in the 2000 serial range which always look new.
If that scope was 8X still, I think the scope by itself would sell for $4000 to $4500 just because of the serial.
I try to get all the guys with real rifles on a facebook group I lead. We always post when early scopes hit the market. They would get excited if this hit ebay. I can hear them now. lol