To wrap up this thread - I had reached out to Sta-Lok through their web contact form just prior to posting here, inquiring about the two part numbers and asking if the current wedges will work in either part. Not really expecting a timely response from them, I was pleasantly surprised to find an email in my inbox this morning which in addition to being very prompt, provided a thorough and complete explanation to my question - copied here:
"We streamlined our part numbers because we just had too many of them doing the exactly the same job
The wedge (part number 126-08) used in the old part number 133-08-5/8 is exactly the same wedge that is used in the 033-08-5/8 as 5/16" & 8mm is exactly the same size."
Also appreciate the response from Dave here at SBO!
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Scott