Tascam M3500 fader metal Panel 8 way There are two oil tubes

There are two oil  tubes for lubrication

These are used widely in all the older Teac models later ones don't have the thread although they should all be compatible in most cases

and sliding switches

though not normally an issue as your taking the old one out

Tascam M3500 fader metal Panel 8 way There are two oil tubesPanel from the M3500 , these are showing signs of age, they clean up not bad but all show some signs of rusting at bottoms or sides simply because the paint has chipped of or got dirty but maybe someone has even worse than these in that case they are useful these are 8 way other bigger listed on its own