NMpistolero: I want to thank you for bringing this subject up as I am currently dealing on another Model 63.
The owner has not yet set a price on his older but minty Model 63 with the 4" barrel.
I bought all my currently owned Model 63's (and a 651!) new, years ago and am in a bit of sticker shock whenever I see a used older Model 63 at a gunshow or in a gunshop!
They do command strong prices.
I would be glad to pay the $620.00 you mention for the minty Model 63 that I am dealing on.
I don't think you would loose much money at all if you paid the $620.00 for your Model 63 and should you decide to sell it in the future.
You might even make a fifty dollar bill.
I hope some more folks will chime in on current values of the older Model 63's.
Hold into the wind
VarmintGuy