The other day I was sorting a bunch of my crystals and came across some old third mode CB crystals. I thought if they work in the third overtone they should work on the fundamental frequency and if fundamental then they will double and if they double I'm on 17meters.
One precaution to consider is that overtone mode is not the same thing as harmonic mode. In third overtone mode, the crystal is physically vibrating at the third overtone frequency, not at the fundamental, and IIRC, the fundamental may not be exactly one third of the marked frequency of the crystal. This probably wouldn't make much difference except near band edges.
...too many 24/7 corntest mode DXers who will call CQ DX endlessly with no response, and when you work them, only have the time to give you just the 599 and sometimes not even a 73...then go back to CQing...sort of like meeting someone at a party, saying hello and then immediately walking away from them....rude....And then there's the "rare DX" stations (like a W5/VP5) working split and hardly ever giving their own call signs so you know what all the ruckus is about....
Exactly the reason I don't go out of my way to chase DX on any band. I agree it is rude. Another analogy of rudeness would be to walk up to a group of strangers standing on the sidewalk having a conversation, and butt in without being invited, especially if you then try to change the subject of the conversation. That happens all to often on the ham bands, and probably contributes to much of the "clannish" behaviour that permeates the lower frequency phone bands, particularly 75.