If that’s a Loto it must be a late one (1998?). All the ones I’ve seen were lugged with a lugged fork and a braze-on seat binder, not the collar type shown here. The seat cluster looks like the one on the 1998 Gap posted by Tuberoaster on p. 2 of this thread. That image is not clear enough to see whether the head tube is lugged or not.
As far as I know, all the Vipers had fillet brazing at the head tube too.