i just saw saw this post and can help... Hopefully you still have this carburetor. It's quite rare and one freaking awesome carb.
The carb IS made by Duratrax, and it's called simply the Duratrax Slide Valve OS Carb. It was discontinued around 1996. The carb was made by Duratrax back when Duratrax parts were made / machined in the USA. -This carb was the "hot ticket" to have.... Liquid-like smoothness, easy to adjust, and freaking SCREAMING top speed. I have 2 of them, both NOS. I searched out my 2 carbs just for "memories" sake. I remember ordering one back in 1993 to use on my OS .12 CZ-2.
It it does look like the high end needle is missing, I honestly can't remember it's been so long! That aluminum "nut" on the end is an adjustment as well.
hope this helps, Jon