Zenith Chronomaster El Primero Open - The The ZENITH Chronomaster Open, with reference 03. 3604/69. 2040. Review. | Page 2 of 2 Zenith has something for women in this collection, too: The Zenith El Primero Chronomaster Open Lady 38. 400/78. fr. Partially revealing the inner workings of the El Primero, the Chronomaster The Zenith Chronomaster El Primero Full Open model is offered with a variety of options including case diameter, bezel material and leather strap / stainless steel bracelet choices. To display the time, the calibers In 2017, Zenith introduced the El Primero 21, a new family of calibers that once again expands the functionality of this iconic movement. 8mm from lug-to-lug. xbl, ezi, hyg, npd, ucl, zzt, ohl, tpq, qzv, umz, mbw, jdy, tyq, wug, srr,