[Heathkit] SB-Series LMO Off 100 KHz?

[jack m]

I finally got into restoring a nice SB-301 that I picked up on Ebay about 2 years ago.  It works fine, aligned nicely and has the potential to be my nicest looking '301.
 
However, the main dial reads 100 KHz higher than the actual frequency on all bands, so I know the het crystals are OK.  The dial has full 5 KHz travel across the bands, and there is no binding or slippage in the mechanism.  When I checked this with my frequency counter however, it read 5.6+ KHz to 5.1- KHz, instead of the 5.507 through 4.997 that I am used to seeing on all my other LMOs.
 
The finger nail polish is intact on both side covers, but the output coil top seal had been removed.  I can't see how this "do not adjust" coil could pull the LMO off by a full KHz.  The LSB/USB offset  adjusted by the book.
 
I have never gotten into repairing an LMO.  Before I take this out to investigate further, does anyone have any ideas about what could have happened in the past?  I'll assume someone diddled with it somewhere along the way, but I thought I'd ask first before removing it and opening it up.  Also, I was wondering what the LMO frequency range would be without the 5-ring tang shaft stop system engaging properly?
 
Thanks  Jack  W3RU