The version is particularly significant in the MAME community. This was a "u" (update) release, meaning it came between official numbered versions. Version 0.139 dates back to around 2010.
This article is a deep dive into Mame4droid 0.139u1 Roms: what they are, why version 0.139u1 matters, where the files belong, and how to build the perfect arcade library on your phone or tablet. Mame4droid 0.139u1 Roms
This is where most beginners get lost. Why is there a number attached to the app, and why do roms need to match it? The version is particularly significant in the MAME
: /sdcard/MAME4droid/samples (used for games with imperfect sound emulation) . 3. Moving ROMs on Modern Android (v11+) why version 0.139u1 matters