Hi David,

Thank you for contacting Mearto with your appraisal inquiry.
A similar version painting was sold at auction in Tampa in 2018; it had an estimate of $150-350 but sold for just $45 (https://www.liveauctioneers.com/item/62242275_-l-thomas-signed-oil-on-canvas-harbor-painting)
Little is known about the artist - I was not able to match the signature on your painting with any "L. Thomas" artists in any of the databases we have access to but several works signed that way - including the 2018 sale of this work - have been offered at auction, all bringing at or less than $100.
Based on the photos and information provided, and subject to examination, this is:

American School, 20th Century
Marine landscape with a boat at a dock
oil on canvas
signed "L.Thomas" lower right
28 by 22 inches, framed
PROVENANCE: acquired at a second-hand store
$75-125*
*represents a fair-market value for auction purposes; retail or asking price may vary.