In addition to the standard Vault of Glass weapons, Light.gg also displays a Timelost version of every weapon. These weapons are visually silver, but are identical in every other way to their base versions.
It seems likely that these Timelost weapons are actually the Adept versions of the Vault of Glass weapons. In a blog earlier this year, assistant game director Joe Blackburn said that Adept versions of raid and dungeon gear would launch alongside the Master Vault of Glass difficulty.
Adept weapons for Strikes and Trials have special mod slots that allow players to increase a weapon’s stats directly. Timelost weapons will likely work very similarly.