Somerville used to date-stamp its manhole covers, so that's how Chris Devers could tell how old this catch basin cover on Washington Street near McGrath Highway is.
Iron Covers, a Somerville resident who takes photos of such things, adds:
They started building the sewer system in somerville right after the civil war because of the population boom. The earliest dated cover I’ve found is 1874. I found one dated 1870 in Cambridge