The two raised surface features are .250-20unc-2b
A metallic or nonmetallic item which is rigid, flat and generally smooth. Its thickness is small in comparison to its length and width. It is designed for mounting another item and may have drilled or threaded holes or other facilities for mounting to a supporting object or surface. See support, as modified. Do not use if a more specific name applies.
NSN 6220-01-190-7542
NSN 5960-00-044-6807
NSN 6685-01-573-1750
NSN 6650-01-477-2124
NSN 6110-00-288-4179
NSN 2925-01-314-5833
NSN 5930-01-062-5847
NSN 5950-00-432-6512
NSN 6130-01-504-1569
NSN 6320-01-422-0765
NSN 5999-01-442-5446
NSN 6685-01-335-0397