Are they ALL DX2-50's?  I'm looking for a
DX-50. 
 I'll double check, but yeah, I am pretty sure these 4 are DX2-50.
 I also have a small stack of 486 CPUs (cpu chip only), and there might
 be a regular DX in there (I know there are some SX and DX2's... as well
 as a few that the chip is glued to the heatsink, so I'm not sure what
 they are) 
 
 If your board can accept one, a DX2-66 performs better than a DX50. The
 DX2-66 only has a 33MHz clock, but if the motherboard has VLB slots, a
 33MHz bus is a must, since anything faster causes timing problems. (A
 40MHz bus can be made to work, but it isn't fun...) If the board has an
 oscillator can or speed selection jumpers, it should be easy to use a
 DX2-66 instead of a DX50. 
 
I am looking specifically for a DX-50 for something special.
Peace...  Sridhar