I found an article in an old French technical magazine La Nature from 1894 about the railway porter made by Martin.
This toy is made in two different versions, a version with the flywheel and a second version with a key wind mechanism both with simulated walking motion.
It was first made in 1894
The length is about 12,7 cm ( 5 inch) long
The Martin production number is 123 for the version with the flywheel and number 124 for the version with the key wind mechanism, see on the catalog page in the left below corner.
A free translation from the text above for the model with the key wind mechanism.
The railway postman. –
Here is a charming tin toy, equipped with an ingenious mechanism.
It represents one of the wheelbarrows used by railway letter carriers; under the wheelbarrow is placed the motor mechanism in the form of a spring that is tensioned by torsion by means of a key visible in our figure.
The mounted spring actuates the pair of toothed wheels.
The man who pushes the car has legs fixed on an axis and which are connected to each other by another bent ace which forces one leg to move back as the other leg advances.
When the device is driven by the motor movement, the postman seems to be pushing the car, and his movements surprisingly imitate nature. –
This toy is built by Mr. Fernand Martin, 88, boulevard Menilmontant, In Paris.