Civil War Spencer Carbine Ser. No.`s

I have a Model 1860 Spencer carbine in the mid 56xxx range. According to Springfield Research documentation this gun was issued to a trooper in Co.E 6th Illinois cavalry. No date is given for its issue.And according to a listing of Spencers by SR it has a date beside this guns no.of July/65 which I`ve been told does not mean date of issue unless stated as such. Otherwise the date represents either Logged in or turned in.
I searched the net for info and I found that this regiment recieved its Spencers beginning in early 64 thru late spring 64.{ no mention of ser.no.`s} My problem is I don`t think this gun was issued and used during the mid to late 1864 period. I believe that guns in this high a serial no. range were not even made till Dec 64 or possibly early 65 and did not make it into the pipeline in time to see any or much action.
Thats why I`am asking if there is anyone out there that may know anything about this and your opinion.