Sounds like these negatives may be valuable. I would be very leary about glass carriers. The emulsion may stick to the glass. Zone VI sells a negative carrier thru Calumet, that may be just what you need.

"4x5 Out-Straight Type 2 Negative Carrier"

Catalogue # EN57455

Designed for large format photographers who require ultimate precision of focus, the Out-Straight negative carrier will draw your negatives perfectly flat. It is also adjustable in negative size to accommodate the larger film pack and Polaroid negatives.