Auction Series 257-264 in Zurich Day 4

Coastal Ships - Borgå Area - Borgå Ångslups Aktiebolag 1900c.: Typeset 20 penni black on orange paper, single outer frameline, BOLAG without stop, perf. 11½ x imperforate, probably printed in sheets of four stamps, a used example on the reverse of entire letter from a lady called Hilda to Fanny Bjorkluna in Leutla (?). Illustrated in Dr. Connell 'The Letter and Parcel Stamps of the Finnish Shipping Companies' on page 107. Unique.
Catalogue 261: Stamp Issuing Steamship Companies