When creating a SNMP Type within the snmp data model the OID string value must match the exact value of your device OID in order to identify the type of device. If i'm correct your OID (188.8.131.52.184.108.40.206.1.6) is the PhysicalAdress of your device so it should be your device's MAC Address.
The problem i've found using the SNMP Data Model is that most of the time the OIDs string value are unique therefore i've modified the SnmpScan module not to check for the exact string but to identify if the OID string value configured on the server is contained in the string value returned by the device.
For example for linux targeted devices, i've configured these values :
- OID = 220.127.116.11.18.104.22.168.0 (SNMPv2-MIB::sysDescr)
- OID String Value = "Linux"
The device returns the string "Linux <hostname> 2.6.18-308.el5PAE #1 SMP Tue Feb 21 20:46:05 EST 2012 i686"
Since the returned string contains my conditional OID String Value ("Linux") the device is identified as a Linux machine.