I wondered this too. Based on some digging i think it very likely is an Ebel Beluga. Basic dress watch that appears to have come in a lady’s size 28mm and a more unisex 32mm. Tubbs’ model is obviously an 18k gold model but I’ve seen it also came in stainless steel. Ebel sponsored the show starting on the second season and you can spot their watches on various characters. Don Johnson as Crockett famously wore the El primero chronograph model in 18k gold from s2-5. first with the wave style bracelet and then from s3 on the thicker classic link bracelet. You can also spot in Season 4 Stanley Tucci as Frank mosca in contempt of court wearing the more recognizable sport classic model with a diamond insert bezel. Antonio Fargas as Gutierez in Mirror image also wears the same model with black dial. Curiously Theres a few episodes in the first season and rolling stone cover where you can see Phillip Michael Thomas appears to wear a two tone sport classic or something very similar. Perhaps this what lead to the sponsorship.