Probably Simson tubes of IZH 50A 4 Ringe steel(Russian).

Without images, I believe all your answers will be found here:

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=172682&page=1

http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=231860&page=all

Kind Regards,

Raimey
rse