A number of responses to the value of a mark on a piece of art glass.

From Randy Blye of Birmingham, Alabama
When I sell or purchase a piece of Steuben with a total value of $100-$1,000 on e-bay I count the signature as an increase in value of $25-$50. I value the post production Frederick Carder signature at an easy $100. The post production signature I consider to be a good value and investment and someday I would like to see it increase in value. I have seldom used the signature as a means of identification. A signature on a seldomly signed piece should add interest. One of my favorites is the diamond point single script “S” found on some Sea Green pieces and late production finger bowls. So……yes. They don’t always pay but I sell the signature and different signatures should have different values.

Charles Sweigart thoughtful comments
Your hypothesis only proves that uneducated buyers rely on a mark to confirm a piece is by a specific maker. This confirms the practice of putting bogus marks on non genuine articles, especially if sold at discounted prices to genuine.

Placing an appraisal value on a piece does not include selling it to an uneducated buyer. The appraisal price assumes the buyer is knowledgeable and willing to pay the current market price or in the case of Insurance replacement appraisal, the highest possible market price is appropriate. All of the bottom feeders are excluded as they will only buy at discounted values.

If one only buys, sells or collects signed pieces of a product that was not always signed; they will never achieve a representative grouping of that product.

In the world of paintings, a single signed piece may be the basis for proving the authorship of dozens of unsigned examples.

In the world of glass making, many products were never signed. Only catalogs of the period or the sweat of the excavators at the original factory sites digging up shards that when compared to whole examples provided proof positive of authorship. Sandwich glass and Akro Agate marbles are two examples.

Another thought from Isidore Cohn, Jr. of Metarie, Louisiana
I have been collecting Steuben since about 1945 – Carder pieces at a later date.

When I first began purchasing major engraved or other significant Steuben items I requested the artist’s signature. It seemed sensible to me since in most fields of art a signature authenticates a work of art and is highly desirable. When I first requested this, Steuben resisted and finally agreed if I paid for the work in advance then it could be signed. I still ask for a signature on any major work and do not see anything wrong with that approach.

Finally, comments from Bethesda, Maryland’s Dick Stark
getting out of hand….some folks ought to collect signatures….i prefer the object.