Dave, I doubt your Dufferin was a snooker cue. Snooker cues are usually ash shafts, smaller diameter than a pool cue, and often have brass ferrules. Do a youtube search on "Ronnie O'Sullivan"...to see snooker cues in action. He's generally recognized as the top snooker player.
You're in California, right? If so, I'd suggest being low key about your Ivory content.
Oregon & California have recently passed some strict laws on Ivory. The maker of highly prized "Gina" cues was recently busted by the feds for selling cues containing Ivory to some Asian guys who got caught by customs with them in their luggage. Ferrules made of Ivory may not be as strong as those made of other materials, so I'd suggest going easy when you break. 5/8"? The ferrules on my Josey are 7/8" long. Very generally speaking, the longer ferrules are used with maple shafts, while "low deflection" shafts use short ferrules. Many versions of "low deflection" shafts made by various manufacturers. The theory being when a shaft is laminated and light in the front there is less cue ball deflection when using English. Some players love the low deflection shafts, some don't. I tried one some years back and I couldn't see any real advantage and I didn't like the feel. Probably because I'm a terrible pool player, nowhere near a high skill level....and I hope to remain a bad pool player for years to come.
Really, it's all a personal taste thing with cues. Cruise the various forums at AZBilliards.com, and you can read debates on joint styles, brands of cues, tips, shaft materials, you name it. Then keep in mind that Shane Van Boening, generally recognized as the best player in the USA, shoots with a Cuetec R360...one of the least expensive production cues. Yes, he gets paid to do so. To a huge extent, it's the indian, not the arrow when it comes to pool skill. That said, there are some awfully well made arrows out there. I'm pretty old school when it comes to what I like in a cue.