Hi Barry, since the fluid has no red color it is probably not ATF and most likely is honey colored. So it could be engine oil or it could be most likely AW 46 hydraulic fluid. AW46 is pretty commonly used in older Monacos. When I talked to Monaco about the hydraulic fluid in my 2004 MH they told me that I could use AW 46 or Dexron III and the big difference was in cold weather operation. Monaco told me that with AW46 the hydraulic pressure could get too high in real cold wether such as in new England and it could burst the hydraulic cooler. I did have AW 46 in my system and it looked like motor oil and have filled it up with Dexron III but I could have gone either way. My manual says to use Dexron but that was not what was in it. Also according to HWH that make slides and hydraulic leveling systems they state that one should use hydraulic fluid but can use Dexron III but the say that the reason they don't use ATF is if it leaks it stains things red. So it appears that AW 46 and Dexron III are pretty well interchangeable. Later model Monaco MHs also used 15w-40 oil in their systems but I have never heard of that being used in the older Monacos. A lot depends on the type hydraulic system incorporated in the MH.
You might find this chart interesting
Severson Oil - Hydraulic Oils