I don't know what lathe you have as the numbers and letters in your subject are neither model numbers or part numbers. But assuming that you need the half nuts for an Atlas built Sears sold 6", 9" or 12" lathe, call Clausing @ 1-800-323-0972. They still stock new ones (or did a few months ago). You can also usually find them on eBay but new originals are usually higher price than at Clausing, or are brass, which won't last as long. And you can actually still get they through Sears Parts Direct. But again at a mark-up.
OK. Could you post a side view photo of the lathe. And a close-up photo or photos of the numbers and letters that you found?
Before you can buy the correct half nuts, you have to know at least what size the machine is. Lathes are usually sized by "swing" and "distance between centers". Swing in the US is taken as the largest diameter that the lathe can swing over the ways. The actual diameter to touch the ways is always just a fraction larger than that. On the Atlas 12" machines, the actual figure is about 12-1/4". In the UK, swing is taken to mean the vertical distance from the top of plane of the ways and the axis of the spindle. So one half of the US convention. "distance between centers" means the nominal distance between the point of a lathe center inserted into the taper in the spindle and the point of one inserted into the taper in the tailstock ram with the ram retracted and the tailstock all of the way towards the right end of the bed. The latter figure is usually rounded down to the nearest inch.