[old_tv_nut]

Actually, I think Zenith used 17 pf, and RCA used something larger, like 22 pf. So search on ebay to see if you can find something like that. But if not, I think the ones cut for 17 will work with a slightly different tuning of A16. The important thing is that the crystal sees the equivalent of the capacitance it is cut for as the result of everything that is attached to it. Crystals tuned for one or the other will change the gain of the control stage, which will affect the pull-in range and transient response to some extent.