This was an option 32 kit for the HP 5526a.
It includes what is shown only.

(1) 10690-60001 Straightness Interferometer Assembly with mounting plate
(1) HP 10690-60002 Straightness Reflector Short Range SN: 1332A00798
(1) HP 10690-60001 Straightness Interferometer Short Range SN: 1332A00798
(1) HP 10691-60002 Straightness Reflector Long Range SN: 1332A00499
(1) HP 10691-60002 Straightness Interferometer Long Range SN: 1332A00499
(2) Micrometer Mounting Stages
(4) Mounting Rods
(2) Wood Cases

Straightness Interferometer Assembly & Straightness Interferometer Long Range have some splatter on the outside of them. It does not appear to be anything that would affect the proper operation.

We do not have the capabilities to test this item completely but we will guarantee it to work properly or we will give you a 100% refund (Excluding shipping) if returned to us within 14 days.