Re: WP&Y container flat trucks

I posed the same question some time ago when I found trucks with that designation under the flatcar with Tank 28 at the YTM in Whitehorse.
Trucks: ESTADO - ASF 21221C 115 x 203 M/M 4-42 AAR38 with 26" dia wheels
Here is the answer from John Stutz:
4-42 is mfg date, ESTADO is the purchasing company's designation, presumably shortened from
F. C. del Estado, or Spanish for State Railway. I've no idea which Spanish speaking railroad originally ordered these trucks, and would welcome any documented evidence. No speculation please!
ASF denotes the well known American Steel Foundry.
21221C is probably the ASF pattern number.
115 x 203 M/M denotes the journal diameter and length, in millimeters, which equals the standard AAR 4 1/4" x 8". I believe this size is the AAR standard for 40 ton nominal capacity cars.
AAR38 probably denotes the date when the AAR testing committee approved this side frame design for service at the nominal journal rating, where all up loaded car weight, LD LMT + LT WT, is typically about 1.5 x the nominal capacity rating.