Dear Eden,
What in heaven would be the purport of such claim? Computers were not only expensive, they involved major investments, certainly machines the size of Pegasus. Hence, the legitimation for making such investment was seldomly based on the single use for one field of application, or rather for one department in an enterprise or university. Historians usually can trace the considerations leading to the actual purchase in the company archives. Also one may be able to guess where (in which subdepartment) the first initiative to such deep investment in modernizing business originated.
How the machine was in fact used, once installed, is much harder to reconstruct. Did the administrative support staff actually get to use the computer or were they pushed out by the scientific computers from the laboratory departments. Were management scientists favored before the statisticians and the down to earth daily bookkeeping? In the incidental case where a logbook is preserved, or where a very early computing center kept statistics, one may be able to tell something about who was using the machine.
So, what could be the meaning of "dedicated to"? Was that "dedicated" on the level of legitimation of the purchase, or was it "dedicated" in terms of seconds and minutes of use of the system? Let alone that we could judge the claim of "entirely" or even "first".
Rather, to us historians being aware of inclusion and exclusion mechanisms around the use of computers, simply power struggles if you will, the claim of "dedicated entirely" made in a first person account has a clear intent. Other users, other interested parties, were succesfully made invisible, at least in the account of the "management science" department. Probably bookkkeeping use didnot count, or was counted under management science in the first place, etcetera.
Rather than investigating the claim, my suggestion would be to investigate the fact that such claim was made, when and by whom.
Best, Gerard Alberts