The first is a square. the rosewood inserts are for insulation purposes to limit distortion when handling.
The second is a sine bar.
The square can be rescued by grinding/scraping and a lot of work. The sine bar can probably be rescued by replacing the tube sections with sections from the same piece of drill rod of an appropriate diameter if there is no corrosion on the body where the tubular sections met it... probably not worth the effort.
Use the salt and vinegar rust removal trick, and afterwards, stick a couple gauge blocks under it. do the trig and measure. Ill bet you dollars to donuts any error will not be of any consideration for hobby work.
Ive seen many items far worse than this cleaned up and doing good service.
Hell..if you dont want it, stick it in an padded envelope, and mail it off to me. Ill pay the shipping. Ive got a sine table, but could use a bar.
No 220-pound thug can threaten the well-being or dignity of a 110-pound woman who has two pounds of iron to even things out. Is that evil? Is that wrong? People who object to weapons aren't abolishing violence, they're begging for the rule of brute force, when the biggest, strongest animals among men were always automatically "right". Guns end that, and social democracy is a hollow farce without an armed populace to make it work. - L. Neil Smith
Hmm ... this one I'm not sure about, but as a guess, it might be intended for checking the angle of a dovetail when scraping it. Depends on what the included angle of the beveled edges is, of course.
However, this one is quite obvious. It *used* to be a sine bar, but with that rust, especially on the rollers, and probably on the top surface (not visible in the photo) as well, it is no longer capable of the accuracy for which it was made.
The rolls should be *precisely* 5.000" apart, and *precisely* the same diameter. The roll on the lower tight hand end (as photographed) rests on a surface plate, and the one on the upper left end rests on a stack of gauge blocks built up with the help of a sine table and the knowledge that the centers are 5" apart. (Multiply the sine of the desired angle by 5, and build a stack of gauge blocks precisely that high to generate the desired angle. The threaded holes are for attaching extra fixtures to the bar, for holding the workpiece, perhaps for use in a surface grinder or something similar.