I am getting different opinions about whether this can be 925 purity (not plated). There is a website that gives examples of the marks Gorham used for sterling silver items and the above is one of them. The site is a popular one and if that example is wrong, it maybe should be corrected. Is it against posting rules here to put a link to that site?
I do not want to put acid on the flask as it is in such good condition.
What is needed is an image of your mark on your flask, embedded for viewing (not a link to it). Reference links are useable as additional material, but never from a site with commercial aspects (ie selling stuff). You'll find it easier than it sounds.
So, yes to date codes on silverplate..not on flatware which may have other codes (weight of plate). Meriden also instituted code cyphers (0, 00) for their plate in that era. Your "Q" would match 1884, assuming it is definitely a "Q" rather than a cypher.