I agree with Frognot and Beto, I would tell the boss that the meat is on the old side, tell him upfront. Let him know you will open it up, check it out, but, that if there is any doubt, you will not cook it.
If I had a reputation as a cook, I would not risk it because some guy thinks that meat is good enough for his workers. To be honest, I would have told him no, I prefer to buy my own meat for what I cook.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."