Hard to get much information on either company. What I know has been picked up in bits and pieces mainly on the Internet. I know very little about Kalmar, just that I've run into a few pieces by the company on the Net and in antique stores. Mazzega is described very briefly in Carl I. Gable, "Murano Magic." The company, I.V.R. Mazzega, started operations in in 1950 as a result of the reorganization of Fratelli Mazzega. Its master glassblowers were Ermano Nason (1953-9) and Pino Signoretto (1959-73), both exceptional artists. The company also had some wonderful designers, particularly in the 1950's. For three years the company collaborated with Fucina degli Angeli, realizing designs by world famous artists.
The 50's were the highlight years and the company eventually closed its doors in 1983, by which time it was producing a fair amount of lighting.
Documentary sources on Murano are very hard to come by especially when it comes to lighting. Venini has some records, but even their lighting records are incomplete. I took a photograph of a chandelier I have around Venice and Murano. People were very helpful, but I was never able to pin down a maker, opinion being divided among Cenedese, Venini, and a couple of other makers. I've learned to love the chandelier whoever made it.
There is still a Mazzega operating at the premises that IVR Mazzega occupied--I've been in the store--but I don't know the connection to the original Mazzega. The new company makes chandeliers , too, but mainly reproductions of older styles. I didn't find them helpful but they might be worth trying by sending them a photograph of your piece.