Just ran across this , is this the only 2100 in existence that had this tube hybrid treatment?
https://m.ebay.com/itm/McIntosh-Tub...390296?hash=item2f0e7ac718:g:CRkAAOSwT2daAfS5
https://m.ebay.com/itm/McIntosh-Tub...390296?hash=item2f0e7ac718:g:CRkAAOSwT2daAfS5