What happened here ? Oscillators missing a part

[Koen]

Hello,

     I took a small gamble the other day by ordering a few major-brand oscillators from a chinese supplier (top) rather than Digikey (bottom). Instead of complete oscillators, I received shields void of the main component (what is it ?).

     Any idea what happened here ? Did someone sell an incomplete and to-be-trashed reel to the distributor ? Was it sold to an assembler who discovered it and later sold it to someone else ? If so, how did it pass factory QC ?

    The shield is correct, markings are correct, pads are correct, it is impossible to discover without inspecting one out of the reel.

     Somewhat related question : are the matte black blobs which are different on each oscillator's shiny black component some factory trimming ?

     I had to order some other components (which major distributors hardly sell) from this supplier and out of the 10 different references, only this one is wrong.

Thank you,
Koen