If I were in the market for a Cuban link chain these are the things I'd be looking for, no matter who you get the chain manufactured from. (in no particular order)
1. Chain must be over karat, if I'm paying for 14k I want 14k +,if I'm paying for for 18k I want 18k+ etc.
2.Links have to be filed the way I want it, you might want it flat on both sides or rounded on both sides, you must relay this to whoever is making the chain, if not you will get what they give you!
3. unless you are getting a bracelet you want the chain to hang straight, no coiling at all.
4.you want the box lock to be properly hand made, with zero gaps in between the male and female portion of the lock (when closed), you also want the distance from the last link to the male & female portion of the lock to be as minimal as possible. if not it just looks bad to have tight links and a huge gap at the last link. The sign of a good lock is that it will not open when pulled on with the figure 8 claps unattached.
5. try to go to your local jewelry store and try different mm sizes and see what fits you. if you cant then add 2mm to what you think you want, links always look bigger in pictures. so if you think you want a 8mm get a 10mm, if you think you want a 10mm pony up and get the 12mm. there's nothing worse than getting the chain and feeling underwhelmed, or having the chain for a year and feeling you need to upgrade.
6.Only personalize the lock if you plan on keeping, if down the road you decide to sell there aren't many takers out there for a chain with your initials/logo on it, keep that in mind.
7. try not to lowball, we all want the best price but if the jeweler you decide to go with tells you $8000 don't ask if you can do it for $7300, they might accept the offer but just know that they will skimp on a portion of making your chain.
8.NEVER rush them, let them know that you aren't in a hurry and that you want the chain done correctly with zero compromise.
9.factor if you will be getting a pendant on the chain when choosing the length, if you get a 28" chain and later on decide to pair it with a 4" pendant don't forget the time machine back to 2001.
10.factor in how you will make the payment, some might accept a bank transfer helping you save on fees, others will only accept payment methods that come with fees. that can easily increase the price by $500-$1000. (don't forget to ask for free shipping)
Wear your chain in good health, but be smart, nothing wrong with tucking it in when you're on the wrong side of town!