Hmmm. that makes sense. It figured the noise on 910 has to do with the 455.
Recently, I have noticed that there were A through F suffixes on the Superadio II model numbers, as I had paid attention only to the "Superadio I, II, III" names. My Superadio III is the 7-2887B (the B version) and my Superadio II is the 2885C made in Hong Kong. I saw on Ebay that some sellers of SRII claim the 7-2885F had some improvements over the earlier SRII's. But I think the build quality on the II may have worsened and the 7-2885F was made in China instead of Hong Kong. So al this makes me wonder how the SRIII 7-2885B compared to the A version and the 2885C compared to the other versions of the Superadio IIs, in terms of RF performance. I found practically no info online about it.
A bit to add to the info here, as I have an SR2 F, made in China in 1991. Up until recently I used it as a kitchen radio, and had not used much for DXing until the last week or so. A couple days ago I compared it side by side with a SR1 (1981) and SR3 (1995).
My Chinese built SR2 is pretty robust, as my cat knocked it off the top of the refrigerator and you can't even tell it hit the floor. Still works fine. Only 'repair' I had to do was straighten the tines on the AC plug, which were bent before the radio the floor.
As to performance, my SR2 works very well; overall it's a hair more selective than my SR1 -- less splash from adjacent channels -- and as good or better for DXing than my SR3 (no whistle on 1340, very reduced whistle on 910). It has better noise reduction than my SR1. More fidelity than the SR3, especially through headphones. Smoother audio through headphones than the SR1. Some of these differences may just be the way the radios were aligned from the factory.
RE: overall lack of specific info on the SR2 models: You're right, there isn't that much info on the differences between the A, B, C, D, E, and F models -- even on the Yahoo GE Superadio group, the info is sort of incomplete. The stereo headphone jack was apparently added during the C or D model. And production switched to China at some point (obviously during the F model or earlier).