you are buying one WD1415M2CIT92L1 made by JDSU
WDM coupler for 1480/1550 nm pumped erbium doped fiber amplifiers
you will probably not get the serial number of the one in the picture.
the JDSU product bulletin says that:
the WD1415 Series WDM couplers are used for efficient coupling of 1480 nm pump sources and 1550 nm signal lasers in erbium doped fiber amplifiers.
contact me and I can send you a copy of the product bulletin. I do not have a datasheet.