17th century architect's compass - photo

[Tonyg]

Look like deviders to me, and agree with mwmkravchenko.

[mklotz]

Look like deviders to me...

Admittedly, they do look like the modern version of dividers but recognize the fact that in the 1600s, the "architect" may have been drawing directly on materials such as stone, slate or metal at the worksite. A scribed rather than pencilled mark wouldn't have easily washed or abraded away.