Ernest Reuben Lilienthal, was born in New York and trained as a lawyer. He learned the whiskey trade as an employee of Freiberg & Workum and became a salesman for them in New York.
In 1872 he moved to San Francisco and set up a wholesale operation at 223 California Street under the name Lilienthal & Co. and selling Freiberg & Workum products. The company grew rapidly to become the largest wholesaler in the west. In 1896, the liquor business was spun off from the company's other enterprises and incorporated as the Crown Distilleries Company, which operated to Prohibition.
Don.....
Source:http://www.pre-pro.com/midacore/view_vendor.php?vid=SFO10927
What size is it? The bigger, the better. No matter the size, Western slug plate flasks like yours are usually rare, and are always in good demand. Some are very rare, the experts at the auction houses can give you a better idea of rarity. Your piece has excellent color and it's nicely whittled. If it is a rare piece, it's value will be increased by a professional cleaning. My gut says that yours is a rare piece.
harpp, a flask just like yours recently fetched $700.00 at auction, lot #136, AmericanBottle auction #48. That bottle was darker than yours, your lighter color is considered quite rare. Your piece is not in as good of condition, but it has great potential if cleaned. Nice find!