Merely for the sake of accuracy, and not of contradiction, JimBob appears to have the right of it: Spencer did not deliver carbines until a lot turned over to the Ordnance Department in October, 1863. Only rifles were in the hands of the troops before then and, getting its first contract for carbines in 1863, the company had first to complete existing rifle orders before it turned whole-heartedly to carbine production, although there was some overlappage. My carbine in the 14,500 range was part of the last 1863 delivery by Spencer to the Ordnance Department on 7 December of that year. Given the serial number of my friend Wormey's newly acquired Spencer, the March, 1863 date must be a typo, apparently in the printed source material. His appears an 1864 manufactured piece, thus delivered to Ordnance no earlier than 1864. In any event, it appears Spencer wasn't yet into general production of carbines in March, '63.