DEP1 file extension - Data Exchange Protocol analysis file
What is dep1 file? How to open dep1 files?
File type specification:
The DEP1 file extension is used for one of the Data Exchange Protocol files. The data exchange protocols (DEP) define logical sets of the complete data at defined stages in the process, from analysis through design and fabrication. A *.dep1 file contains analysis data.
Seems like it was used in the past in some 3D engineering software.