Just a note about taking derailers fully apart, it's better not to turn the limit screws any more than necessary, lest any plastic thread-lock pieces get worn away by the threads.
The plastic is old and likely shrunken already!

I also agree with the others that this derailer's design doesn't appear to emphasize long-term durability.
Used gently, in a clean environment, it's likely going to be fine, but dirt/water and/or hard use is going to invite trouble.
Bumpy roads may fracture the fragile A/B pivot springs, dirt/water will eat up the pulley bushing and pivot surfaces, and hard shifting may break the locator link rod.