I don't know about the latest production mantles. The last time I bought new ones was 10+ years ago. I think they were being made in England at the time. Where are these being made and who is selling them? Aladdin Mantle Lamp Co. is probably the distributor.
I live in South Florida where it is all but impossible to get bulk kerosene so I don't use my Aladdins much any more and my mantles last for a long time. The only mantles I have left are NOS from the 1950s and I am using them rather than buying new ones. I once bought a full store counter dispplay box, a dozen IIRC. They apear to to hang straighter and burn more evenly than newer ones. BTW: I only use original B burners, no 21s or 23s.
Don't buy NOS wicks - they shrink over time and won't fit over the inner wick tube. The circle of tape inside the wick is what shrinks and it doesn't have any stretch to it at all. I've had som bad experiences with them. I keep a few wicks around but they are all relatively new.
I just looked at aladdinlamp.com, the company wwebsite, ane their R150 mantles look just like any others I've seen.
I've been collecting, restoring and using Aladdins for many years and would welcome PMs on the subject, either questions or general discussion.
Also see
http://www.aladdinlamps.com/
Jim