1913 Romanov Tercentenary 50k frame only die proof in dark grey-green, with the names of designer and engraver beneath the picture, very fine, signed „PMD“. Possibly from Tsar collection R. Lowe 1935 as described “50 kopecks: … Fifty-seven die proofs of the frame in different shades …” published in the Yamschik-Post Rider 1983, No 12, page 15.