Date/quality of Jupiter 846R without alphabetical prefix?

[notecracker]

One of these horns has come available locally.

I checked the serial number and apparently it doesn't begin with a letter, it's six numbers beginning with 5.

Does this mean it's an older less well-built model?
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RIP Maurice, 1933-2012. The greatest.

[MacMichael]

You might want to look here:
http://www.jupitermusic.co.uk/rdas/papp.asp?cmd=FADE&DocumentID=2838&TemplateID=83

And yes, the older generation of Jupiter horns has had a notorious reputation...