Keith's is a mid 30's model, it's got 14 frets to the body & a slightly different shape to the earlier models which have 12 frets to the body. I have a 1933 model O, 12 fret, & I personally like the way it 'sits', I'm not comfy with 14 fret models, but that's my personal opinion.
I've also got a tricone made by Greg Beeton, north of Sydney, you can see a pic of it here, it's the one on the extreme right.
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www.jefflang.com.au]
It's the first one in which he engraved the back & sides as well, he basically copied the design from Brozman's book.
You can play a single cone comfortably on your right knee, but tricones just feel better (to me) when you've got them on your left knee, like a classical guitar, that way you angle it so it faces you a lot more. Resos project their sound straight out so I find when I've got it in my lap I can hear what it's really like. A good idea when buying one would be to take a guitar-playing friend along & sit in front of him as he's playing it, you'll notice the difference in sound from when you're playing it.
For strings go for phophor bronze, 16-56 or so, immediately ditch the nickel strings the asian ones come with, I always tune down to a G or D, with thinner strings you could tune up to A or E, but I like the feel & weight of the thicker strings.
For slide, if you want metal, go to a hardware store & buy a spark plug socket which fits whichever finger you're going to use, make sure you can put your finger all the way in, some sockets only go 1/2 the way in. For glass, scout around for a wine bottle that fits your finger, put it in several thick bags & then just smash it against something hard, after 2-3 attempts you'll get it. When in Canada I used 'Light-n-Easy' cider bottles, they came in a 6-pack, nice brew. Forget ever having to buy a commercially made slide.
There's a difference in sound between the nickel-plated brass ones, which have a 'sweet' tone, & the galvanised steel ones which are definitely grungier much more suited to down home delta blues. Nickel ones look a lot better on stage tho, make sure you polish it to really catch the light.
The advice about replacing the cone on the asian models is a sound one & I'd scout around & have it done professionally if you're unsure about it.