ATSF Steel Caboose query

I am puzzled about a small detail that appeared on ATSF steel cabooses since the first ones built in 1927 (by AC&F, 1500 class). It is a small vertical metal "hanger" (for lack of a better word), two on each end, one to the left and right of the end door just inboard of the vertical grab irons.

These appear to have been an "as built" feature yet I do not know what they are for or what they were called. I thumbed through Stephen Priest's excellent reference book, Santa Fe Waycars but found no reference to this hanger. There were a couple photos of early cars with what appeared to be rolled up stacks of waybills stuffed in the hangers to hold them. Perhaps this is how station agents and/or clerks left waybills for conductors at certain points? They look like a great place to hang a lantern too. I have received some feedback from ATSF crewmen on what they actually used these for (waybills, lanterns, fusees) but I have been unable to confirm what the as-built purpose was.

In many cases, these hangers survived well past the rebuilds and until many of these cabooses were retired. In the two shots below, one is of CCT 24 (ex-ATSF 1547) which shows both hangers. The other is a close-up of the hanger which is on retired ATSF Ce-1 999110 which now resides at Travel Town in Los Angeles.

If you know the story behind this appliance, please drop me a note at:

Thanks!

Mike