This is used to correlate PE's with their corresponding PerfMaps. For example the header in the perfmap could be:
```
FFFFFFFF 00 026D4D21B3EE3D93843FF7A964235822
FFFFFFFE 00 1
FFFFFFFD 00 1
FFFFFFFC 00 3
FFFFFFFB 00 1
```
And the PE will have the corresponding entries in the PE as:
```
PerfMap (Type 21):
        System.Private.CoreLib.ni.r2rmap, Signature = 026d4d21b3ee3d93843ff7a964235822, Version = 1
```