An OBJECT_FORMAT structure wraps a pointer to a QUEUE_FORMAT structure ([MS-MQMQ] section 2.2.7).

 typedef struct OBJECT_FORMAT {
   [range(1,2)] DWORD ObjType;
   [switch_is(ObjType)] union {
       QUEUE_FORMAT* pQueueFormat;

ObjType: This value MUST be 0x00000001. The value 0x00000002 is defined for local-only use and MUST NOT appear on the wire.

pQueueFormat: This MUST point to a QUEUE_FORMAT structure.