This is what John wrote after sending Him a couple of BS silvers.I don't know if it would apply to proofs though.
"I have processed the coins that you submitted for attribution in a package postmarked April 16, 2016.
The doubling that you see on the obverse of the two 1973-S Eisenhower dollars
is the result of a doubled master die. At the beginning of a given year a master die is produced with the coin's design for that year. Hundreds of working hubs are then produced from the master die. The working hub is then used to produce hundreds of working dies. The working dies are then used in the coining presses to strike the coins. If there is doubling on the master die, then all working hubs produced from the doubled master die will have the same doubling. In turn, all working dies produced by each of those doubled working hubs will also all have the same doubling. In such cases all of the coins produced that year will show the same doubling with some minor differences due to hub and die wear. You can access more information on doubled master dies on my website http://www.doubleddie.com
by clicking on Doubled Dies in the left column menu and then scrolling down until you find the link for Doubled Master Dies.
The doubling on the reverse is even worse as it traces back to a doubled master hub. The master hub was created for use over a period of several years. Each year the master hub would be used to create a master die for that year. If the doubling can be traced back to the master hub, that doubling will be found over a period of several years. In this case the doubling that you see on the reverse of your 1973-S Ike dollars
can be found on all 1973, 1974, 1977, and 1978 Ike dollars
making it way too common to have any value.
I hope that this information helps.
Good luck with all of your collecting efforts.
John A. Wexler"