I don't have access to the SRS information to perhaps offer more details, but your serial number 143581 is listed in Mallory's as being issued to Co. G , 2nd USV Engr.  There are quite a few others listed to several other Companies in that Regiment.  Many can be found in the 143,000 range, but there are many others in the range between 142000 and at least 146000.  I found only 2 numbers (145168 and 145169) that were consecutive numbers.  There may be others, but having so many issued to more than one Company, would seem to indicate an early issue on a unit basis rather than simply replacements. I expect that we will find more information about this unit's history.  It's always fun to see some history unfold about pieces we own, so stay tuned boys and girls.