OB.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the OB.H header at

d:\th\minkernel\ntos\inc

and draws from it the following type definitions:

Line Number	Type	NTOSP.H	NTOSIFS.H
147	struct _OBJECT_DUMP_CONTROL	43868	1402
157	enum _OB_OPEN_REASON	43878	1412
303	struct _OBJECT_TYPE_INITIALIZER	44024	1488
347	struct _OBJECT_TYPE	44068
381	struct _OBJECT_DIRECTORY	44097
393	struct _OBJECT_DIRECTORY_ENTRY
404	struct _OBJECT_SYMBOLIC_LINK
422	struct _DEVICE_MAP
437	struct _OBJECT_HANDLE_COUNT_ENTRY
446	struct _OBJECT_HANDLE_COUNT_DATABASE
479	struct _OBJECT_CREATE_INFORMATION
494	struct _OBJECT_HEADER	44111
556	struct _OBJECT_HEADER_PADDING_INFO
560	struct _OBJECT_HEADER_AUDIT_INFO
565	struct _OBJECT_HEADER_QUOTA_INFO
575	struct _OBJECT_HEADER_HANDLE_INFO
582	struct _OBJECT_HEADER_PROCESS_INFO
592	struct _OBJECT_HEADER_NAME_INFO	44171
623	struct _OBJECT_HEADER_CREATOR_INFO
634	struct _OB_HANDLE_REVOCATION_BLOCK
1110	struct _OB_DUPLICATE_STATE

The header OB.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).