One Belt for Pugio and Gladius

[A_Volpe]

around the time of the introduction of seggies, we start to see baldrics being used?

Yup. That seems to be the general [accepted] consensus, based on what little bits of info we have.

On a side note, I have a leather tie that I've looped through between the two bottom plates on my seg. on my left
side and use that to tie the belt. It does help prevent the belt from falling down. I also try to "hook" the bottom edge
of the belt to the first brass lacing loop on the Seg. as well as try to have the belt as 'tight' as possible.

There was some experimenting done with what were colloquially called "Marius clips" based on a [random] archaeological bit found that was a small piece of metal bent into an "S" like shape, that seemed to fit well between Seg. plates and had been interpreted as a kind of "belt hook / keeper", not unlike the ones seen on some modern uniforms.
Of course, we have no real idea IF that's what the hooks were used for, but they did seem to work really well for some.