The energy colossus that is Con Edison of New York emerged from the competitions, mergers, deals, finaglings and plenty of 'boodle' extending back to the Consolidated Gas Company of 1823, in 1936. Wikipedia reckons that 170 different companies went into the making of the company. For lid-lovers it marks an end point for 7 electric companies - NYE, UEL&P, BECo, NY&QEL&P, WLC, & SIE, the gas company itself Consolidated Gas Co, and the steam provider NYSC. The CT&TSCo Ltd. was a wholly owned subsidiary of Con Gas, and thus Con Ed, but kept its own identity until 1961.
The design for the earliest Con Ed Company covers is identical to the long standing covers used by the precursor New York Edison Company. (see example below). What is most interesting is that this design served as a skeleton for the formation of one of the most widespread designs seen on the streets of NY, the concentric rings of circles of the "Con Edison" cover.
In the 1930's New York Edison and then Con Edison were still providing DC current to lofts and buildings that required it. It's last DC customer was cut off in 2007. This may have been a remnant of that system.
There are not too many Con Ed covers of this type, I have only found two. This one is at the busy intersection of 57th St and Lexington Ave. and the other is on Varick St. near the Holland Tunnel.