Do you have a Listed door closer 236N?  If you do you  probably have a Corbin Russwin Door Closer.  The sticker or stamping usually says Listed Door Closer Arm 236N.  This is the UL number, which is a testing laboratory.   UL stands for Underwriters Laboratory, which started in 1894, to test electrically and fire equipment.  It does not tell us which door closer you have, but it narrows it down.   Another number we find on closers is 149A and 320 G, which are also UL numbers.  The best way to proceed is to find out as much as you can about the door closer you have.   I would look for Manufacturer (Corbin Russwin, LCN, Norton, Yale, International, Sargent, ect..), possibly a model number,  the hole spacing of the hydraulic cylinder (3/4″ x 9-1/16″, 3/4″ x 8-3/16″, ect…),   how the door closer is mounted (on the door, top jamb, push side, pull side).    If your hole spacing is 1″ x 4-1/8″, then you most definitely have a Corbin Russwin DC3210 or DC6210.  You can find the Corbin Russwin Door Closer on our website.  If you are still confused, call and speak to our door closer expert.