Watch specifications state magnetic resistance in gauss rather than in the SI unit. Neither source cited here is a watch source, so no marketing figure is quoted in this entry; what follows is only what the metrology bodies publish about the unit itself.
The SI coherent derived unit of magnetic flux density is the tesla (T), listed in the SI Brochure as Wb/m², or kg·s⁻²·A⁻¹.
The gauss does not appear in the current SI Brochure at all, and is not among the non-SI units listed there for use with the SI. It is a CGS unit.
The conversion, from NIST: 1 gauss = 1 × 10⁻⁴ tesla. So 15,000 gauss is 1.5 T.
A wording caution. The current Brochure contains no blanket sentence forbidding units it does not list, so "BIPM deprecates the gauss" is not a supportable claim. What is supportable is that the gauss is not an SI unit and is not listed among the non-SI units for use with the SI.
Sources
Every statement above traces to one of these. Read on the date shown.