Please explain the differences in doubling

Geoman

Anyone,

I have read many posts about doubling. Sometimes, the answer is that it is "machine doubling" and not worth much of a premium. So what is machine doubling? And what other types of doubling are there? What types of doubling are worth more than others?

Thanks!

XpipedreamR

This may be of interest to you:

Linky-Dang-Doodle

Geoman

Cool site. Thanks!