A machinist's model of a twin cylinder steam engine designed by Joseph Bernays in the 1870's. The original was displayed in Paris at the Universal Exposition of 1878.
@Dave-R Got it! Thanks Dave...it did seem like overkill to lock both the viewport and the layers, but it seemed like one of my viewports was shifting (even though camera positions weren't changed) and I thought maybe I had been double-clicking into the viewport(s) w/o realizing it. Still not sure what I did, but it seems to be working now.