Submarine chaser SC 282 was commissioned at Mare Island on 22 April 1918, and served in the Canal Zone.
These photographs are from the collection a crewman on SC 282, and were submitted by his grandson, Mike Stephenson. Note especially the exceptional shot of the wheelhouse, possibly the best one I've seen.
The Y-Gun photo shows the detail nicely: A blank charge would be inserted at the base, to launch the two depth charges.
The photo showing chasers with "For Sale" is interesting as well. This might be a bit of humor, but in fact after the war there was an effort to sell the chasers rather then bring them back to the U.S.
Thanks to Mike Stephenson for submitting the scans to The Subchaser Archives.