From the now defunct Lockheed Twin site: "At least two basic versions of the Learstar were eventually offered. The initial version was the Mk 1 which was powered by R-1820-76A engines, at 1425 hp. With standard and long range models being offered depending whether one opted for the 470 USG (1,779 l) or 696 USG (2,635 l) wing tank held in Lear's modified outer wing. The first flight took place on May 19, 1954 with deliveries commencing in 1955 to Butler Aviation Co of Chicago, Illinois, USA (N16L c/n 2508), conversion time was approximately 4 months."
According to The Lockheed File, this aircraft may have been involved in drug running at one point in its life, under a different registration.