Our group companies include Gebrüder Martin, Karl Leibinger Medizintechnik, KLS Martin in Freiburg, Stuckenbrock Medizintechnik, Rudolf Buck and KLS Martin in the USA as well as numerous subsidiaries and representative offices all over the world. The two oldest group companies are Karl Leibinger Medizintechnik and Stuckenbrock Medizintechnik. The family companies have existed since 1896 and 1884. Our youngest offspring is our subsidiary KLS Martin de México, which we founded in 2019.
In the last 15 years alone, ten subsidiaries and representative offices as well as our first two production facilities outside Europe in Penang, Malaysia, and Jacksonville, Florida, USA, were opened. In addition to founding new subsidiaries, we have also constantly created perspectives for an innovative future for the existing companies. The most recent project is the expansion of our production facilities at Karl Leibinger Medizintechnik in Mühlheim an der Donau. With an investment sum of around 13 million euros, the extension represents our largest single investment to date in more than 100 years of the company's history.
Together, we have more than doubled the group's worldwide sales in the last ten years. This growth is also reflected in the number of our employees. At our marketing and sales company Gebrüder Martin alone, including its subsidiaries and representative offices, we were able to increase the number of employees by more than 82% in 15 years.
In addition to our international expansion, we have also invested in new technologies and markets. Our entry into vessel sealing in 2005, LED technology in 2008, modular OR systems in 2011 and additive manufacturing in 2014 paved the way for subsequent product innovations.
These include our vessel sealing system marSeal, our SonicWeld Rx® system for the insertion of resorbable implants, our marLED® V and X series and the expansion of the indications for our patient-specific implants IPS Implants®. These are in addition to maxillofacial surgery now also available in hand surgery.
Our products are intended to support the user throughout the entire process and not just as a partial solution. For this reason, we offer our IPS CaseDesigner® software for virtual 3D planning and simulation of orthognathic procedures and IPS Gate® as a communication platform for communication between clinical users and our implant designers. Software is also a topic that will accompany us in the future, which is why we have invested in our strategic partner CADS GmbH this year, as part of our digital strategy.
A comprehensive support for clinical users and our specialist trade partners also includes a well-rounded training and further education concept. Between 2016 and 2019, we opened two training centers for this purpose at our locations in Tuttlingen and Jacksonville, Florida. In our KLS Martin WORLD in Tuttlingen alone, around 2,000 events have taken place since the opening of the building and we are already looking forward to all future events. In addition to our own training centers, we also focus on the further development of training concepts with our scientific partners.
Even though we love to look back on the last 15 years of the KLS Martin Group, we are all the more looking forward to the future and everything new that we will create as the KLS Martin family!