I have four 2500K here. Batch L051A869, SN are 2L047225A1607,1608,1609,1610.
For 24/7 use they all clock exactly the same (4800 1.34v, 4900 1.38v linx) but max bootable multiplier is different on all four chips (using exact same settings): x52/x52/x54/x51
my personal view: batch for maximum overclock = witchhunt