Help ID bolt markings

[colreed]

Top flat bolt is H U. There does not appear to be a . before the U.
Middle flat bolt appears to be either a V or a triangle with a weak bottom leg. Could be an upside down A.
Bottom bolt is round. Appears to be a O B. No sign of an A before the O.
Hope the picture comes out OK.
Any help appreciated.
Regards
Reed

Information

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[Newscotlander]

Part of the problem is that you have parkerized bolts which means that they have been refinished. I'm not sure about the top one, probably Underwood. The middle one is IBM. What you are seeing is an upside down letter A. There should be an AOB stamped on the outside of the right lug. It may be a weak stamping the was eroded off during the refinishing process. The bottom bolt is marked SB. It is an IBM bolt made by the Standard Computing Scale Company.

[painter777]

Bottom round bolt.......maybe SB, for late IBM.
Still thinking about the other 2.

Charlie-painter777

[painter777]

Nice work Chris !

Charlie

[lbelflowers]

HU bolt-possibly Howe Machinery Co. for Underwood