A Foster lightning style mason jar, with only "Sealfast" on the jar, instead of the usual "Foster Sealfast". 

It is in good condition. 

 Foster Glass was an American company that produced glass canning jars with the label "Foster Sealfast" during the late 19th and early 20th centuries. The company was founded in 1850 in New York City and was known for producing high-quality glass products, including bottles, jars, and containers.
The "Foster Sealfast" label was introduced in the 1880s and became synonymous with the company's high-quality sealed glass jars. These jars were designed to keep food fresh for longer periods of time by creating a vacuum inside the jar, which prevented bacteria and other contaminants from entering. The unique design of the Foster Sealfast jars made them highly sought after by housekeepers and cooks, who appreciated their ability to preserve food without the need for preservatives or refrigeration.
Foster Glass continued to produce the "Foster Sealfast" line of jars until the mid-1920s, when the company began to shift its focus towards the production of automobile windshields. While the "Foster Sealfast" jars are no longer in production, they remain a valuable collectible item for those interested in vintage glassware and the history of food preservation techniques.