There's at least one more truck with the Markel symbol on Shorpy. See it here.

The sticker on the truck that "Vonderbees" asked about is from Markel Service, Inc. Markel insured buses and trucks starting in 1930, and it was also involved in promoting safety and standards for drivers. The firm also helped to pass the National Motor Carrier Act of 1935. The firm exists today as Markel Corporation, and it is a Fortune 500 company.

As a part of their program to promote safety, drivers were given safety awards for each year that they did not have an accident. A variety of these awards and award certificates is shown below. The pin with number "1" in the red diamond is believed to be an early award as few of these are known to exist. Awards in the style of the 4-year pin shown seems to have followed, but these were likely awarded for only a short period of time as these are also very hard to find. Pins in the style of the 15-year award shown were issued into the 1950s, and the 20-year award was the last style issued.

The other side of the Dodge truck is seen in the photo below. The truck is from 1940, and this was the first year that the Dodge cab-over truck body was entirely designed, engineered, and built in-house. The previous three years the body was manufactured by Montpelier Company of Montpelier, Ohio. The 1940 models are easily identified by the lack of cowl lights which were on the 1941 and 1942 models. In this initial year of production 1 1/2 ton and 2 ton models were available. The cab could seat three, and it was up high enough that the floor of the cab was flat. The directional (turn) signal lights are mounted on the fender tops, and a Dodge ram hood ornament is visible.

Eastern Auto Forwarding of Buffalo, New York had orange trucks with green lettering. Their motto was "Dependable As The Rising Sun." They once had a fleet of 385 rigs, but by 1964 this was reduced to 50 as the railroads became a more efficient means to transport new vehicles. The firm was bought out by Buffalo based M&G Convoy in 1964.

Is this a GMC cab over?

[Dodge. -tterrace]

I remember seeing trucks with that sticker having an "M" inside the shape of the US. Does anyone know what that signifies?

I've never seen one like this either but I found a pic of a similar setup with open sides.

Too much Dodge on the outside for it to handle.