The IWC 'Skinny' Ingenieur SL Automatic 3505 came out in 1983 as a smaller option to the 'Jumbo' SL from 1976. It has a 34.00mm case and runs on an ETA-based self-winding movement, known as caliber 375. This specific model, reference IW3505-13, features a stainless steel case with a 14k yellow gold bezel and a matching bracelet. The dial is a classic silver color.