A PAGE OF USEFUL LINKS RELATING TO COMPASSES & SCIENTIFIC INSTRUMENTS
INTERPRETING ENGLISH SILVER HALLMARKS
THE COMPASS COLLECTOR (SINGER'S PATENT)
U.S. NAVAL OBSERVATORY ASTRONOMICAL INFORMATION CENTER
HOWARD SUN COMPASS DISC ONLINE CREATOR
PYSER OPTICS - FRANCIS BARKER COMPASSES
SIRS NAVIGATION (G-150 COMPASSES)