Are these the Dx lever's predecessor? They are built like crap, I'm used to shimano stuff being top shelf quality stuff. Any info on these?

You know what? I just realized they dont say shimano anywhere on them, knockoffs, thus explaining the built like crap part.

Are the letters on them "MX"?
I know Shimano had the "MX" line just before the "DX" stuff.

No idea if they had levers in the line though.

actually shimano levers werent any better. I had a pair as a kid. i always had a dime under my handlebar pad to keep turning the adjuster screw back out.

Plain Shimano MX at best, most probably Taiwan junk. I have a whole bunch of them.

Shimano MX and DX levers came out at the same time. MX just happened to be a lower line