2N4249
PNP Si transistor, TO-106, Fairchild S035928
Used in DC503 as Q545 and Q548 (depending on S/N and option - pdf pg 48, AKA 7-10)
Equivalents
The Sphere Tek cross-reference indicates that 2N4249 is equivalent.
Additional searching on the internet finds various sites stating that this Tek P/N is NSN 5961-00-246-2427. Searching that number will lead to 2N4249 (same number as Sphere provides) as well as 2N4429 (note the similarity - likely a transposition). The latter is incorrect, as that is an NPN RF power transistor and not in TO-106 package.
Specs
Exact specs of the 151-0342-00 are unknown. The 2N4249 is 60V, 0.1A, hFE 100-300.