The R540LTD had, I believe, a Wizard neck which differed from the standard R series at the time. No idea on the H&S or the 01R bits though!

~Edit~ it was 92 that they put the Wizard neck on the R540LTD, but if it's a late in the year 91 it'll be build to 92 specs. I have an RG770DX with a 91 serial number and 92 specs along that line.