mickey rat: The Junior matrix numbers are also stamped alongside the Ember ones in the runout groove.
Juke Jules: The Silhouettes were W. (Bill) Horton, Richard (Rick) Lewis, Earl Beal and Raymond Edwards, so KB's info was accurate.
According to Gonzalez, Junior 391 was released in 1957. Ember E-1029 was released in November 1957. The ABC Goldies 45 2485 reissue was released on 15th June 1973 and your guess is as good as anybody's when Lost Nite 254 and Collectables 1495 were released, although the latter was probably in the 1980s when Collectables changed from Lost Nite. There was a 1964 Lana 108 version of this single, but it isn't listed whether the tracks are reissues, alternate takes or re-recordings.
The ARSA website lists this record as Hit Bound on WWCA Gary, IN in late December '57. The January 6th 1958 edition of Billboard lists the record as among 'Recent pop releases coming up strong' while the 45cat Ember discography list's Ember E-1027 as being a November 1957 release so all in all 'Get A Job' looks like a December '57 release.
Catalog number should be E-1029. Ember files say recorded at Beltone, mastered(?) at Longwear, but it came out first on Kae Williams' Junior label in Philadelphia first so I dunno. Matrix numbers on the Junior release were K-593 and K-594. The Ember matrices were E-2172 and E-2173.