I sure would not doubt your Grandfathers estimate on your clocks age, I can only relay what I found in my reference materials.
I found a similar clock to yours (everything the same except the painted picture on the tablet) and the date of manufacturer was 1875.
The value of that model was approx. $450.
Other visitors may know more.
Response to Comment Left by: mike
Thank you for your response, I hope others will respond also.
Where is the paper label printed? by: Anonymous
I have a similar clock, but with a different painting, and I have researched the company that printed the paper label, versus the Seth Thomas Company. The paper was printed by The Case, Lockwood, Brainard & Co. Print, Hartford, Conn. The key to this is that the Case, Lockwood, Brainard & Co. dropped the Co. in 1868.
Also Plymouth Hollow was renamed Thomaston in 1865, so therefore, my clock was made between 1865-1868. Prehaps your clock was too.
Seth Thomas steeple clock by: Independence, MO
I have a similar clock except the picture on front is of a bird. Otherwise appears to be same. The clock was purchased by my great aunt in Nettleton, Mo. Would like to have more info.