Reply To: Childhood air gun without piston seal.
From the crude looking piston, I would say Chinese origin. Doesn’t look threaded so seal was probably pressed on. An adapter kit and seal are available from Vortek, but you may have to resize the hole and tap it for the adapter screw(usually metric).
Link here for 25mm
Not sure it would be worth the money and effort if it is a 20.00 Chinese rifle though.