Additionally, it demonstrates innovation by the railroad for repurposing an existing boiler in 1928; for a cooperative effort of three Colorado companies to reverse-engineer an existing class of locomotives for which the D&RGW already carried a quantity of replacement parts; and, in 1947, for adding thermic siphons to boost steaming efficiency and increase heating surface within the firebox, a practice not previously applied to narrow gauge locomotives.  In effect, D&RGW Locomotive No. 491 is the "test case" of applying these boiler improvements, common on standard-gauge locomotives, to a narrow-gauge locomotive.