Well, just a little thing, the drawings on my gondola actually had the chalk marks 'XPKD OYO 11-10-46' listed on the car sides, and similar dates(1946-47) on the other cars. I'd assume that was the latest point they had been shopped at the time the drawings was made. I do hope they stayed true to their '20s forms at that time though; otherwise all of my NG consists for the last several weeks have been time-travelers. Good to hear you've got more of these cars in your sights, as I'm moving straight on, already having started a mesh for C&S #6. But as for the trucks, I'm sorry to say I only made two versions; trucks are not my specialty.
It's RPKD, not XPKD. RPKD is short for repacked, when the journals were cleaned out and fresh cotton waste (or pads, depending on era) were added. OYO in that string is the station where this was done: Owenyo. The two other dates which might appear on the sides are the reweigh date, which is on the same line as the LT WT, and the built (or rebuild) date, which is typically listed near the dimensional data. The reweigh date also includes the station where the car was weighed (probably OYO in this case.) Car journals were repacked and cars reweighed about once every 30 months, so these dates were usually changed without cars being repainted. All the railroads did was paint a patch over the old number and stencil the new date over the old one. If you want one more stencil, the brake cylinder or reservoir should have a COT&S stencil which says what railroad last maintained the brakes, where the work was done, and when.
While I don't know much about the SP narrow gauge's freight cars (especially in regards to rebuild dates or when paint schemes changed), you can pretty safely make the RPKD, reweigh and COT&S dates older if you want to represent an earlier time. Those were standard from at least the 1920s on until consolidated stencils were introduced in the 1960s.
258, and in the case of the RPKD thing you're probably correct, the info is drawn on the drawings, and not listed on the side. Don't know if I'll change it as the letters are so small you can't hardly read them anyway. Ah well, gotta remap the smokebox and then redo the freight car colors, and add noise.
Also got C&S moguls in game...Shots on that soon.
Oh, and BTW if the boxcars and caboose look a bit brown...I accidentally made them a little transparent.
Oh, fine, I'll show the whole thing.
She's got adjustable doors and roof hatch, lifting oil and water hatches, animated bell, toggle-able marker lights and flags(not got the markers to light yet) and beautifully operating cylinder drains.
...yeah. Cylinder drains.