Mellotronists

Look at the difference between the control knobs of the "SA Mellotron"
pictured here in the "photos" section, and the knobs pictured on the
clear plexiglas Mellotron that just went up for auction on eBay. I
just found a set of the kind on the clear 'Tron in the bottom of my
unit. Mine are like the SM machine. Which ones are the originals?

By "set", I mean the three identical round pitch, volume, and tone
knobs, and then the track selector.

New 'Tron discoveries for the week: FischerSpooner (Capitol), and
Ak-Momo (Hidden Agenda)