St. Petersburg Football (Soccer) League
1915-16(?), pre-printed cover addressed to Rostov-on-Don Football Society, endorsed "registered" and franked by 50k lilac and green, unidentified dotted "mute cancellation",horizontal fold did not detract, part of a postmark on reverse, VF, it's not guaranteed to be genuine postal history item, however presented envelope with Football League pre-print is very rare