The ".part1" extension signifies file segmentation. "Gran Turismo 6" is a massive game, clocking in at over 15GB uncompressed. In the early 2010s, when internet speeds were slower and file hosting services had strict upload limits, large files were "split" into manageable chunks (usually 1GB or 2GB each).
Knowing your setup can help me provide specific file placement instructions. Gran-Turismo-6----All-DLC--BCES01893.part1
This is the title identifier. In the world of "scene" releases and file archiving, the name is often simplified and hyphenated to ensure compatibility with various operating systems and file transfer protocols that might struggle with spaces or special characters. It signals the core content: Polyphony Digital’s sixth mainline entry. Gran-Turismo-6----All-DLC--BCES01893.part1
That’s why you might have stumbled across a file named: Gran-Turismo-6----All-DLC--BCES01893.part1