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 5945-01-037-7721
NSN 6105-00-222-4762
NSN 5930-01-589-4114
NSN 5996-01-512-0800
NSN 6240-00-982-6748
NSN 7035-00-205-8739
NSN 5915-00-113-4396
NSN 5920-01-146-4503
NSN 7035-01-633-9537
NSN 6685-00-720-3525
NSN 5965-01-042-2001
NSN 4140-00-012-3506