Rare 15D road marker in Morton Grove

Here's a rare find that is located almost under my nose here in Morton Grove. A 15D road maker on the southwest corner of Main and Gross Point

And what is 15D?

From the Lake County web site:

This was in accordance with the "15D" section of the motor fuel tax laws. These laws stated that if a county built a road in concrete, it went to the state for maintenance.

I'm not sure what that other numbers mean. They are, I believe, "47, 0103, 1937." The last number clearly has to be the year the marker was erected.

The Lake County Department of Transportation has a 15D marker in front of its office. Perhaps this marker, which is in front of a private home, should stand in front of the Morton Grove Historical Museum.

Many thanks go to the Forgotten Chicago Facebook group for ascertaining the meaning of this marker.

As for the decay in the concrete, most likely it is the result of decades of road salt meant for the surface of Gross Point Road.