Suricata

The following rules do not error in Suricata 3.2.1 or Suricata version 4.0dev (rev 3ff5dc3):

alert tcp any any -> any any (msg:"DUAL SID TEST"; content:"10dc303535874aeccc86a8251e6992f5"; sid:3031; sid:3031; rev:1;)

alert tcp any any -> any any (msg:"DUAL SID TEST"; content:"10dc303535874aeccc86a8251e6992f5"; sid:3032; sid:3033; rev:1;)

It appears to pick the latter one when presented with two:

09/12/2016-14:51:13.407898 [**] [1:3033:1] DUAL SID TEST [**] [Classification: (null)] [Priority: 3] {TCP} 172.16.71.200:42439 -> 172.16.71.162:88