[Elecraft] Buying Second Hand K3S

[Ray Spreadbury]

I have been offered a 100W K3S serial number 10598, at a reasonable price. 

However if my memory serves me right there had to be some factory circuit
mods soon after introduction? This K3S was built from a kit here in the UK
but had to be returned to the distributor with a fault "on the 10W board"
which was replaced apparently.

Does anyone know what were the circuit mods in the early K3S & should I
avoid this particular K3S?

73 Ray G3XLG