Here are some pictures of mileposts on an SP line that had both narrow gauge, electric interurban, and standard gauge lines.
It's interesting to speculate what these might mean. But does anyone happen to have access to the SP's milepost manual?
I have found the following letters:
A
B
C
D
G
L or 1
M
In the attached pictures, the top number is definitely a milepost but it's not the actual mileage in nearly all cases. It's just a post located somewhere within that mile.
Thanks for your help but please no attacks, trolling, or guff.