As you can see signature, it’s John Marin. I found information that yes he did do some woodblock paintings. I have told by a gallery owner yes this is a lithograph. You can easily see in ten time magnifying the raised paint and also the fine cracking throughout the painting. The paper painting is attached to an art board. I did a ph test to the mounting board and the test indicated the board was acid free. The question is what was the artist involvement in the creation of this piece. Did John Marin have his hands on this piece or was this made by someone else using the original block or possibly making new blocks. The cracking of the painting throughout should indicate it is an older piece. It’s odd that the total measurements are not a standard size, this piece would require to cut out a margin to mount in a standard frame, it should be 18” x 24”. This piece would not fit into a standard frame. Probably the artist cut this paper. Does that mean anything? Any more information needed let me know. This should be an important piece of art, If an original this should be quite valuable. Does have some surface damage. Top, right of center, you can see some impression and damage. Also some surface stressed areas.

18.5” x 23.75”