On Monday, August 30, 2004, at 02:43 PM, Beckert, Shawn wrote:

This image of SLBM 17600 was posted in the latest group
of "Fallen Flags" material. I was struck by the small
size of the MoPac herald. When did they change to the
larger herald that I'm more familiar with?

http://www.rr-fallenflags.org/acfx/slbm17600asw.jpg

Also, note that the tack-boards on the door appear to be
painted black. Was this MoPac standard practice, and how
long did it last?

Shawn,
The 25" MP "buzzsaw" emblem was used until mid-1949, when it was then replaced with a 42" size along with the "Route of the Eagles" slogan. Black placards and route card boards were standard on MP (also very common on WP) throughout the 1940s and '50s. Note just the wood portion was black and the metal frame was painted freight car red (or different colors to match the yellow door and gray or blue ends if on Eagle Merchandise cars), unless the painters got sloppy.
Regards,
Ed Hawkins