Samsung 4GB DDR3-1333 ECC Unbuffered UDIMM, 

part number M391B5273CH0-CH9, with HP part number 500210-571.

Confirmed specs:

• Capacity: 4GB
• Type: DDR3 ECC UDIMM
• Speed: 1333 MT/s
• PC Rating: PC3-10600E
• Rank: 2Rx8
• CAS Latency: CL9
• Voltage: 1.5V
• Pins: 240-pin
• ECC: Yes
• Registered: No — this is Unbuffered ECC / UDIMM
• Samsung P/N: M391B5273CH0-CH9
• HP P/N: 500210-571