Those rifles were sold under a number of trade names - Marla, Jelly, Telly, and a few others. They were generally quite strong shooters, and were of quite robust construction. All the ones that I have had apart had leather piston seals. These can be "revived" if not too badly dried out. If you are in need of a new mainspring, check Princess Auto for one of their "machine gun springs" - it is about the right diameter, and can be cut to length to suit.
Thanks for the info, I have most of one that needs repair. Missing stock, trigger guard and cocking arm that goes in compression tube.
Mine is in otherwise clean rustfree condition and is .22 cal
You got me thinking I need to fix it
Walter...