Valve Histories

Globe valves typically carry a two-digit year stamp near the bonnet, preceded by a mold letter indicating the foundry—M for Mole, D for D&H, etc. Early Mole valves (pre-1940) used a recessed oval mold mark, while post-war versions shifted to raised dies. When the date coincides with building construction or major remodel, the valve likely remained original. Cross-reference with architectural records; a valve dated 1928 in a 1925 building may indicate a later upgrade, not original install.

Gate valves often embed their date in the valve body’s underside, stamped during forging before machining. Look for a two-digit year with a superscript letter—A for afterthought rework, R for rethreaded. A valve stamped '42R' was reconditioned during wartime metal rationing, meaning original threads were replaced with standard NPT. Ball floats, rarer and usually in high-end fixtures, may include a pattern number on the stem cap; this can be matched to catalog archives to determine if parts are interchangeable with modern equivalents or require bespoke machining.

Ball floats—especially those with brass bodies and porcelain caps—frequently have a manufacturer’s logo and a single-digit year (e.g., 5 for 1935 or 1955, depending on pattern). In Boston, 1930s-1940s floats often use a patent date from 1920s, meaning the valve is a later cast of an older design. When upgrading, avoid modern plastic floats unless the operating pressure and thermal expansion match the original specifications. Matching the original valve’s stroke length and seating angle ensures consistent water level control without overfilling or cavitation.