Jack:
it's good to see you posting here on the Forum. My apology for not yet responding to your e-mail message.
"Your" Monaco (shown on the top photo) appears to be similar to one that one of our readers sent to Switzerland, for authentication. I agree with Ralf, in terms of the estimates of value. $2,500 would seem like a reasonable price for this one. It's also a matter of personal preference: do you like the "classic" white registers on blue dial OR do you like the blue-on-blue?
Apparently, this version, with applied markers / blue registers. was made late in the life-cycle of the Monacos.
Interesting that both the samples shown here have the same spots / patina near the markers. I might have guessed that it once had applied markers, which were then removed, but I suppose not.
Thanks for the message and photo.
Jeff