As of 4-Jan-2022 [PC]

CPF001 (open on PaulC's bench): 
MB s/n 01
For sure has:
-Mods to CPF MB to replace I2C buffers
-Mods to CPF MB to support LHE board
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5

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CPF002 (open in GeneM's lab):
MB s/n 07
For sure has:
-Mods to CPF MB to replace I2C buffers
-Mods to CPF MB to support LHE board
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5

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CPF003 (closed in test tank room).  Below is based on photos taken on 9 and 10 July, 2020:
MB s/n 05 (photo 20200709_165516)

For sure has: (photos CPF25 and 20200709_153431 and ...39)
-Mods to CPF MB to support LHE board

For sure has: (photos CPF23 and more so 20200709_163632):
-Mods to CPF MB to replace I2C buffers

Unknown, but as of 9-July-2020 did NOT have: 
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5

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UNINSTALLED SPARES
MB s/n 06 (dev spare on Eric Martin)
For sure has: 
-Mods to CPF MB to replace I2C buffers
-Mods to CPF MB to support LHE board
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5

MB s/n ?? (Taken from Gene's Office)
For sure has: 
-Mods to CPF MB to replace I2C buffers
-Mods to CPF MB to support LHE board
Did Not have:
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5
-Serial Number

MB s/n ?? (Taken from Gene's Office)
For sure has: 
-Mods to CPF MB to replace I2C buffers
-Mods to CPF MB to support LHE board
Did Not have:
-Mods to add RC snubbers to U4, U5, D7, Q3, Q5
-Serial Number