I think you will find a few posts that agree with yours that Hamburg Technic is Chinese made and as your measurements discovered of low quality. Check out the *********.com's list of quality parts vendors. You can just google search those words and should get a hit.

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'89 260e (212K Mi.), '92 400e (208K Mi.), '92 400e (not a misprint) (146K Mi.), '95 C220, '81 240D--Sold