This device is mounted next to Lock 10 on the old Chesapeake & Ohio Canal, near Cabin John, Maryland.  I think it opened & closed a sluice gate that would flood the lock to raise the canal boats up, as they travelled up the Potomac from Washington.  Unfortunately, the canal fell into disrepair & stopped being used in the early 20th century.  But it was made into a national park, and some of the locks & aqueducts are maintained as historic tourist attractions.

I took this photo with my Sputnik on Provia 100F, around sunset under a cloudy sky.  I think my exposure was 2 seconds.  I carried a digital SLR with me to serve as my exposure meter (and to take a few 2D photos & cha-chas.)

–Paul Gillis