"A small number of pistol-carbines very similar to the Springfield Model 1855 pistol-carbine described above was manufactured at the Harper's Ferry Armory."
[Date of manufacture is uncertain, but best evidence points to 1853-1854]

"No data is available as to the number made, but the issue was certainly small and probably experimental, possibly being the pattern followed later in the Springfield Model 1855."

Two paragraphs follow which describe the Harpers Ferry pistol-carbine.

Several pages on the Springfield version. Total produced = 4,021. "The pistol-carbine, however, was never popular with the cavalry. . . . the men had but little confidence in the arm." P 87

Large number in armories suggests that either they were never issued or returned from the field, having been replaced by other firearms. The National Firearms Mueseum says this weapon had a 'brief" service hsitory.
http://www.nramuseum.com/the-museum/the-galleries/a-nation-asunder/case-36-arms-for-the-union-union-carbines/us-springfield-model-1855-pistol-carbine.aspx

No mention found in Firearms of the Confederacy, Fuller and Steuart.