I searched all of the records for SN 19854 and 198542 and found nothing that went to a Trap Grade.
SN 198542 - 12 gauge Field Grade 1942
SN 19854 - 12 gauge Fulton 1919
SN FWS19854 - 20 gauge Field Grade 1947
I searched the Miscellaneous Records (several thousand serial numbers in seemingly random order with many made at the transition from the Hunter Bros.) with no record even near the two possible serial numbers.
It appears that I am not going to be of any help to you. However, I would like to see a photograph of the serial number on the water table and/or on the barrels and forend. Something may come to mind when I see the numbers and how they were stamped.