Closely matched pair of Western Electric JW5842 high-mu triodes. (Equivalent to 417A) One tests 27520 uMhos (production code 852), the other 27200 uMhos (production code 652) with a baseline of 16000 uMhos. Believed to be new old stock but will be packaged in white tube box. Tested on Hickok AN/USM-118B.