Immerse a small chip - about 1" - in denatured alcohol. If it dissolves, it is a water-based acrylic. If not, immerse a small chip of the existing coating into a solvent blend of 75% mineral spirits and 25% Olympic No. 1108 SOLVENT or Xylol. Wait 30 seconds and rub the chip between your thumb and forefinger. If the chip dissolves, it is a synthetic rubber-base coating.
If the chip does not dissolve, then immerse the chip in 100% Olympic No. 1108 SOLVENT or Xylol. If the chip then dissolves, it is a chlorinated rubber coating. If it does not, it is an epoxy.
Use the same type finish for refinishing. REMEMBER that a synthetic rubber base coating can be applied over a chlorinated rubber coating but a chlorinated rubber coating cannot be applied over a synthetic rubber. However, you may convert old rubber base to epoxy by first applying FUSION PLUS Conversion Coating.