Thank you for the photo.
It clears up several questions in my mind. It got me to look once again at the on-line Los Angeles County recorded land subdivision maps. At this location the PE had a 60' R/W that was next to and N-W of a 40' R/W that the SP once had for its Duarte Branch. The SP line was on the alignment of the narrrow-gauge San Gabriel Valley Rapid Transit -- this was changed to s.g. in the early 1890s by a lessor and then the property sold to the SP a couple of years later. The SP abandoned its track here in 1942.
The caboose did not arrive until after the war. The SP car record book reports that 467, renumbered 402 - at least on paper - on 12-14-46, was vacated (retired) by the SP in February 1947. The record has the notation "Donated by Pres. Mercier to Mr. Lyon of The Pony Express Museum." Photos after its arrival show it on the track behind the combo.
Prior to 467's retirement it apparently had problems with one of its trucks. There are Post WW-2 pictures of the car on the turntable tail track at Owenyo with one truck missing and that end held up by car stands. It is believed that car #12 contributed one of its trucks. #12 received a pair of freight car trucks.
Brian