I have a different theory now. Having acquired another 53310A, as well as a 54501A for parts (PS in particular), I now can see 3 different Revision PS boards J, L, & E. They do not seem to correlate chronologically with the age of the instrument. I think maybe HP had a huge stockpile of these supplies, and used them, in no particular order. My original 53310A is of the first generation (Made in U.S.A.) circa 1988, (Rev J PS). The latest one, from what I can tell, Made in Korea, 1997 date code marked on the Lithium backed NVRAM (Rev E PS). The scope, was mfg'd early 90's if I remember correctly, and using a (Rev L PS) . I do not know what changes were made in each Rev.
The latest manufactured 53310A came to me with the earliest Rev PS. (Rev E)
So the Rev E supply has no signs of leakage, smell, or corrosion.
The Rev J supply has no signs of leakage, smell, or corrosion.
The Rev L supply from the scope is basically a swamp of sticky, stinky cat pee smell, and corrosion to the screw heads, some circuitry corrosion around the smaller components. It appears it was stored on it's left side (CRT side down), because the swamp was draining out that side, even down the 20 pin connector and cable. The L Rev board also had a look of a shiny coat to it everywhere, and a darker green appearance. Possibly some kind of conformal coat.
Considering all this it makes me think, there may have been some bad production run/s on these caps.
Wouldn't be the first time. It would be interesting to know the Rev levels of other PS boards in these instruments, and the conditions of the boards.