I have a 1972 Super Bass head thats vitually immaculate having been in storage since new. Annoyingly the original owner sent it back to Marshalls to have the Lead / Bass switch fitted, no big deal, except now the amp is up for sale and all the American buyers want full documentation of this - Huh? Yeah, I'm sure Eddie van Halen kept all the paperwork for his amps in, in a handy box to light his cigarettes with - you get the picture!
Does Marshall keep records of works performed on amps? Its serial number is SB / A1593D
Regarding your question it would depend on the date it came to the factory, if you can provide us with the date or month/year it came in for repair and the name and address it would have been booked under we can check our records.