Russian Empire - Principality of Finland. Helmet Solberg (M17, M1917, Solberg, Fin. Sohlberg) - a combined-arms protective steel helmet of the Russian army, and then the Red Army and the Finnish Defense Forces, which was developed, produced and entered the troops during the First World War. Solberg helmet used, in all likelihood (judging by the color), by Finnish fire departments.
Size 56-57. The helmet is an old Finnish alteration.