I have a pair; thats a good price if they are as good condition as you say. If the horns and drivers work and are original there is nothing to look for, I would just buy them. Different years and serial numbers have some more desireable drivers but none of them are weak. It is very hard to recommend something like the 19's; if you know what they are then you already have an opinion. They are the best of the vintage speakers in terms of sound quality and if you like music.. well thats what they sound like. live music. They have beautifull tone. I have found them to be very amplifier sensitive, so be aware of that when you committ. They don't excell at a lot of the audiophile approved behaviours; imaging, soundstage, all that. But damn; they do play music. There is a ton of personal opinion on these speakers, for some reason everyone is an expert; but when you hear them you'll know right away if you want them. Just try and use a reasonable amp; preferably low power tube of good quality for the audition.
Russell C is very knowledgable concerning Altec speakers, maybe he will chime in.