[Ron Ramirez]

I know schematic says not used on all models.. But how do you know what models it was used on..

Simple...first look it over carefully. Does your radio seem to match the early or late schematic? Does your radio have any 35/51 tubes, including one as audio amplifier? If so it is a "late" version (above S/N B22000). Otherwise it is an "early" version (below S/N B22000).

At some point in early 70 production, capacitor (40) was removed as the bean counters at Philco deemed it unnecessary. As to when, I do not know. We could figure it out, but it would require everyone owning an early 70 to be willing to share their 70's serial number. As you know, that isn't going to happen, so why worry about the little things? Just know that your 70 was likely built after the bean counters declared that part (40) in your set was not necessary, and was no longer installed.

Edit: Steve answered as I was typing, and his answer is better than mine. Ditto what he said.