Box Beef from Packers are only dated with pack date. When the grocery butcher does his breakdown, his label computer puts the sell, use and freeze by date on the label. It is only pre-pack stuff like bacon, sausage, hot dogs, pork tenders, etc, that has a sell by date stamped or printed on the package.
Six weeks is the typical time it will hold vac-packed. Keeping really cold <36°F, you could get 8 weeks. Sealed and cold there is some bacterial stuff going on, very slooowly but there is also enzymatic changes. These tenderize but also add a bit of increasing funk that not all are used to. When you open the pac it will have smell but this should dissipate in a minute or two. If fairly strong from pushing the limit, a wash will usually help. If after a wash it is still just nasty, you waited too long.
You should have no issue going 6-7 weeks, from pack date, then unpack and wash, dry and hit it with a heavy coat of rub containing salt. This can buy another 5 days kept cold as possible...JJ
