Is this a 5 gallon size? I should know this, but just double checking. Thank you !

10” in diameter x 17” tall is 1335 cubic inches
1 US gallon is 231 cubic inches

A cylinder with your dimensions is a little over 5 gallons (5.77 gallons)

Hope this helps

10 x 20, 10 x 19 and 10 x 18 were all used on Mae West 5 gallon pumps, according to my contact at Wayne Pumping Systems.

Thank you. This old lady has it, so who knows if she measured it right. I am pretty sure it is 5 gallon. Thank you again.