That 4-8-2 M1 in the foreground is sporting a coast-to-coast tender (larger fuel capacity tender).  Pennsy being the 'Standard Railroad' used like-for-like parts on various classes of locomotives.  In the above photo, the boilers on both the I1s 2-10-0 and the M1 4-8-2 are identical boilers.  Thanks for sharing another historical photo.
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Late in the game for steam; the last PRR fire was in three months. 
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