MIT MI-330: How to tell for which impedance it is?

A fellow on eBay is selling two pairs of MI-330 Shotguns (item# 170113210639). But he doesn't know for which amplifier's input impedance they're optimized. (He claims to be the original owner, btw.) FYI, he has a few pictures of them posted there.
This raises the question: How can one determine this--and not just in this case, but in any case--especially if one doesn't know (or, at least, can't verify) the history of the cables? Are there some sort of markings?
Who can show me how clever they are by looking at the 330s on eBay and determining whether they are for high, low, or medium input impedance amps? I'm looking to get a pair to drive my YBA (27k), which I'm using as a bass amp on Martin Logan Sequel II's woofers.
Btw, I only need one pair. Anyone wanna go "halfsies"?
(PS: I'll be away from my computer until sometime tomorrow, but will be able to read responses, then.)
Glad to help. MIT 330 Shotguns have a shrink marker on the downstream side (that's the shorter RCA) this shmarker will read "low output", or medium, or high. If the input impedance of your YBA is 27k, then the ideal match is LOW, but if you were to get Medium, the performance difference would be only 2% to 3%.
Best of luck,
The 330s I had were cleary labeled (high, medium, or low) on one side of the "magic box". The other side just said MIT cable or something generic.
Nietz - grab em, I used 330 medium (if they aren't marked at all they are tuned to medium) to a 10K input amplifier and a CJ preamp with a sliding input impedance and tried 330 low back and forth and noticed no difference.
The so-called "MIT 330 Shotgun"s listed on eBay aren't really Shotguns (170113210639), it appears. They don't say "Shotgun" on them, just "MI-330 Audio Interface Cable", nor do they have network boxes, just long black bulges, and, with no impedance indication, either. I looked at some pictures of MI-330 Shotguns. And they don't look like them. I have some old MI-330s. And they don't have bulges. So, I don't know what the ones on eBay are. I don't even know, if they're real, or fake. I think that I'll be holding on to my money a little longer.
Thanks for your responses so far.