Maybe this should go under Herdware, but because it is just a link (not a real post) I put it here.
Anyway, I found this page which lists all kinds of info about CBM monitors... you can view info by model#, release date, and "power" (120 or 240 volts, which usually means NTSC or PAL standard).
Has nice comparison chart of supported video modes, and truly massive "visual database" which includes photos of the monitor, types of connectors, video modes, schematics, user guides, FCC info, and more.
(Ray Carlsen is given credit for several pieces of information)
I learned that my favorite monitor was not actually a 1902A! It seems I had a different "marketed for CBM" monitor made by Phillips (the same folks who made the 1902A). This is because there are some differences in the User Guide between my monitor and the 1902A.... For example, my monitor also allowed Analog RGB with a switch on the back; and the front of my monitor had controls for width/height/position. However the similarities are easy to spot... like the 40/80 column switch and "ultra-green" switches on the front of the monitor (I don't know any other monitor with these).
Good point nonefornow, you can't trust a photo... you might get better image by tweaking the contrast/brightness (etc.) controls of the monitor.
I can't say this is true for your case (1084S-D1 versus -P1), but often (usually?) hardware with subtle changes in "model number" often have subtle changes in real features... in other words, both are probably functionally identical... maybe one has a few more/less controls (or inputs) than the other? We'll probably never know unless somebody (who owned both) writes a post