Golden Gate was made by the Homer Laughlin China Company from the late 1890s until the very early 1900s. The shape was largely discontinued after 1903, but pricing catalogs still had three treatments offered on Golden Gate in 1904 and 1905. By 1906 the shape was no longer listed in any HLC catalog.
Pieces are generally marked with a Golden Gate and eagle over lion HLC backstamp. As with most HLC lines, casserole lids will have the treatment number either hand written or stamped in gold.
A special "Laughlin China, Las Flores" marking can also be found on casserole lids. Las Flores refers to a series of treatments. Based on the pricing catalogs, Las Flores might be a specific underglaze pattern that came in different colors. Below is a portion of a 1902 catalog showing Las Flores on the Golden Gate shape (treatments 436-439) and two (500 and 500X) on the American Beauty shape.
Besides Golden Gate and American Beauty, Las Flores markings can be found on Rococo and Colonial. Shapes that followed, namely Seneca and King Charles, don't have Las Flores in their pattern listings.