Here is a quick overview of each release of SCOM and the related version code:

You can check your core version by running the following query against your OpsDB.
select DBVersion from __MOMManagementGroupInfo__

Have a look at the version of your SCOM component files such as HealthService.dll to determine your UR / CU level.

SCOM 2012

• RTM:   7.0.8560.0
• SP1:     7.0.9538.0
• R2:       7.1.10226.0

SCOM 2012 R2 Update Rollups

• UR1: 7.1.10226.1009
• UR2: 7.1.10226.1015
• UR3: 7.1.10226.1037
• UR4: 7.1.10226.1046
• UR5: 7.1.10226.1052
• UR5: 7.1.10226.1052
• UR6: 7.1.10226.1064
• UR7: 7.1.10226.1090
• UR8: 7.1.10226.1118
• UR9: 7.1.10226.1177

SCOM 2007

• R2 RTM:      6.1.7221.0
• R2 RC:          6.1.7043.0
• R2 Beta 1:    6.1.6407.0
• SP1:              6.0.6278.0
• RTM:              6.0.5000.0
• RC:                 6.0.6246.0

SCOM 2007 R2 CU versions

• CU7: 6.1.7221.110
• CU6: 6.1.7221.99
• CU5: 6.1.7221.81
• CU4: 6.1.7221.61
• CU3: 6.1.7221.49
• CU2: 6.1.7221.15
• CU1: 6.1.7221.13