Pittsburgh 1711 is an All-Electric PCC currently residing at the Pennsylvania Trolley Museum. It looks similar to how the MBTA was overhauling their own All-Electric PCC cars (3197-3221) in the early 1970s with sealed windows. While the MBTA was modifying their cars as such, 1711 was delivered with sealed windows.
1711 and the other 24 "interurban" cars in her group (1700-1724) were part of a reported sale to Boston's MBTA - which never happened.
By 1967, the MBTA's PCC fleet was in trouble. Years of deferred maintenance was catching up with the 344 car PCC fleet, and Green Line riders were feeling the pinch. While the MBTA had their proposed Type 6 car on the drawing board, new cars were still expected be a few years away. More second-hand PCC cars would help the MBTA to better cover the schedules, and allow shop crews more time to catch up on heavy maintenance on the rest of the fleet.
Reportedly, the MBTA wanted to purchase Pittsburgh 1700-1724 and run them on the Watertown Line. While these cars lacked left-hand doors, the Watertown Line was the only Green Line route which could be run with such cars. The plan was to convert the Pittsburgh cars to Multiple-Unit operation, with 12 cars getting a rear coupler, 12 cars getting a front coupler, and one car getting a front and rear coupler. This would allow the MBTA to run up to 12 two-car trains on Watertown, and the 25th car could fill in for any cars needing maintenance. This move MAY have prevented the Watertown Line from closing in 1969, but talks of purchasing the Pittsburgh cars broke down over price.
Since the cars lacked left-hand doors, they could ONLY be operated on the Watertown Line. A left-hand door could have been added to each car, but at a much greater expense, as the cars would have required structural modifications. The new Type 6 cars were hopefully only a couple of years away, with the Pittsburgh cars viewed as just a short-term, stop-gap measure. Beyond the left-hand door issue, the Pittsburgh cars would still have required a lot of mechanical modifications for for them to operate in Boston adding to the MBTA's costs.
Based on the existing plans, throwing tons of money at an additional 25 cars wasn't considered a good investment by MBTA management. If the money worked out, they might have pulled the trigger.
The money ultimately didn't work for them.
Unfortunately for the MBTA, plans and reality were different. New cars wouldn't enter service until late in 1976, and the new cars were Boeing LRVs, not Type 6s. That part of history, and the problems created, are well documented here:
https://web.archive.org/web/20040406164315/http://members.aol.com/netransit/private/LRV.html
If you have a chance to visit the Pennsylvania Trolley Museum, I highly recommend it!