References:
Illustrated Catalogue Issued Annually by Thos. H. McCollin, Thos.
H. McCollin (Philadelphia, PA), January 1, 1876, p. 26
Catalogue of
Photographic Lenses, Consisting of Peerless Portrait, Darlot Portrait,
Morrison's Landscape, Condensing Lenses, &c.,
Scovill Mfg. Co. (Waterbury, CT). dated 1876, pp.3-5.
The Philadelphia Photographer Vol. XI No. 126
in "Class in Landscape Photography" (June, 1874), pp. 174-5
The Philadelphia Photographer Vol. XI No. 127 (advertisement listing
the sizes and focus) (June, 1874), ads p. 120
The Philadelphia Photographer No. 158 (February, 1877), page 141
The Photographic Times, Vol. 10, No. 115, Scovill Mfg. Co. (New
York, NY), July 1880, p. 165
The Photographer's Friend, Richard Walsl (Baltimore, MD), 7th
edition, 1882, p. 40