TT engines generally say "ABC" on the box, but are in fact ABN. Story was that they had the boxes and were not interested "truth in advertising". On the good side, their nickel plating is (claimed to be) much thicker than that on OS engines. Some folks report OS nickel plate tends to be too thin and wear or peel.
The only OS .46LA I have run was from a very early run, bought at the Puyallup Model Expo (Winter) right after they became available, and it has been and still is a very nice engine. Its first gallon of fuel was Powermaster 10-29 all castor, then 10-22 half synthetic. I haven't run it since VSC in 2009, but have no reason to think it's clapped. I've run it with a MACS Muffler and a Randy Aero "CNC Tube Muffler", but never the stock muffler. Mostly on an 11.5 x 4 APC, but also a 12.25 x 3.75 butchered down to 11.5"....and a full 12-5 APC for a few flights.
Steve