The OP says nothing about this being the W-2 of an S Corp shareholder or a relative of such.

In the old days, it was quite common to have have medical paid post-tax.  The amount in Box 1 included the wages which ultimately paid the medical insurance.  I haven't seen it in probably 3 decades plus but back in the early 80s it  happened all the time.  In fact, and I may be wrong on this, but IIRC the law allowing pre-tax on the medical wasn't passed until the late 70s.  I believe the business had to proactively do something to make the deduction pre-tax. Someone feel free to correct me on this.