I found an item which says “the [Sumpter Valley] company is building new refrigerator cars and cabooses,” in the East Oregonian (Pendleton), Vol. 17, No. 5037 (May 2, 1904), at page 1, Col. 2 (Sumpter Extension, ¶ 4), at, [
oregonnews.uoregon.edu] (Aug. 30, 2016). In view of what is known, this report suggests that Sumpter Valley Caboose #3 was built in 1904.
As background, the S.V. Ry. had had only 2 cabooses as of June 30, 1897, presumably ##1-2 (according to Poor’s Manual of Railroads for 1898, at page 273, at, [
babel.hathitrust.org] [Aug. 28, 2016]). By June 30, 1907, the S.V. Ry. had 3 cabooses, presumably ##1-3 (according to 1st Report of the Railroad Commission of Oregon (1907), at page 172, at, [
babel.hathitrust.org] [Aug. 27, 2016]). Finally, the S.V. Ry. did build its Caboose #3, (according to Sumpter Valley Ry., Valuation No. 103, schedule of Sumpter Valley Ry. freight train cars [Interstate Commerce Commission, 1916] [“Caboose Cars – Nos. 2 and 3: [built by] S.V. Ry. Co.”]). For these reasons, Caboose #3 appears to have been included in the reported 1904 S.V. Ry. car building.