For sale is a cardboard sign measuring 10 and 3/4 inches square marked "DANGEROUS" in red and "HANDLE CAREFULLY". The top left corner reads "Form 748-3, The N.Y., N.H. & H. RR Co." indicating this card was used by the New York, New Haven & Hartford Railroad. I have not been able to locate another card with this form number and I'm estimating this is from the 1940's.
The New York, New Haven and Hartford Railroad (commonly known as the New Haven), (reporting mark NH) was a railroad that operated in the northeast United States from 1872 to 1968 which served the states of Connecticut, New York, Rhode Island, and Massachusetts. Its primary connections included Boston and New York.
The card has darkened somewhat around the edges and there is a light stain on the back. Please see photos for additional condition details and don't hesitate to ask questions. Thanks for looking.