Based on a teaching intervention with modelling activities involving experimental work in 9th grade classes, the goal of this study is to find out how students estimate the credibility a modelling task setting when it integrates a hands-on experimental approach. The theoretical background is based on the concept of authenticity and its long tradition in mathematical modelling and inquiry-based learning and advances a path of discussion around the concept of credibility. This is done in close connection to the relevance of experiments and hands-on activities in mathematical modelling in line with a science, technology, engineering, and mathematics approach. The students were assigned the task of creating custom colour paint, responding to an order from a customer in a paint manufacturing company. The empirical data were collected from the observation of two classes and a questionnaire after completion of the task. The results indicate that students viewed the event as credible, as well as the goal of the task. They also considered the experimental work to be necessary and found the mathematical model obtained to be feasible. Moreover the students showed awareness of a distinction between their experiments and models and those developed by professionals. In short, the students ascribed credibility to the task setting and were able to acknowledge an approximation to reality in both the prototype created and the model built.