The Trolley Museum of New York in Kingston had posted an enigmatic message on their Facebook page a few days ago hinting at a mysterious new acquisition, and today the curtain was pulled back to reveal - Metropolitan Atlanta Rapid Transit Authority 510, the newest arrival at TMNY. The photo above, taken by Marc Glucksman of River Rail Photo, shows the car being switched into the museum by their Brill doodlebug.
MARTA 510 is identical to MARTA 509, which was donated to the Southeastern Railway Museum in November as described here, and is from the system's original order for subway cars. It's a single-unit car, so it's double-ended, and appears to be preserved in complete condition. Car 509 had been in storage since 2007, so the same may be the case with 510 but I don't know; either way, it looks very nice and may have been spruced up by MARTA shop forces, as was the case with 509 before it went to SERM.
MARTA 510 seems a bit out of place at TMNY. Although the museum is no stranger to rapid transit equipment (before 510's arrival, six of the organization's nine electric cars were from the New York area rapid transit network), this is the only piece in its collection that isn't from New York or a state adjoining it.* In fact, it may be only the second piece of equipment TMNY has ever owned that isn't from the region around New York (after North Shore 411, which the organization sold off way back in 1973). However, the car appears to be in good condition; has likely benefitted from the milder Georgia climate and (presumably) lower career mileage than most subway cars from closer cities; and is far more weather-resistant than the museum's older cars, making it a better candidate for outdoor storage and display. There's nothing wrong with seeing a second Atlanta rapid transit car preserved.
*Except for some foreign cars, admittedly