My name is ***** ***** I would be happy to help with your grandparents' ashtray.
Thanks for the two photos, actually you attached two of the 'naughty' side (rather than one of each) but I know exactly what the top side looks like. The lady is looking startled and there's an "OH!" to the right of her head and therefore this piece is often referred to as the "OH!" ashtray". There's also a rarer version where the man is saying "AH". The "OH!AH!" version sells for slightly more.
This novelty piece first appeared in the 1920s during the days of the speakeasy and was copiously reproduced until the 1950s when they reached the peak of their popularity. Most are made of spelter, or pot metal, sometimes anodized to look like a gold or bronze finish and some of die-cast zinc (which looks to be what yours is) . There were also versions made in earthenware, and true bronze or brass though these are rarer.
Although quite old there are still quite a lot of these about on the secondary market as they are virtually indestructible, so prices are not that high for them. If you were to see the "OH!" version for sale in an antique store it would have a retail value of about $60. (Add 20% if you have the "OH!AH!" version). These are also the replacement values for insurance purposes.
Expect to get in the range of 30% - 40% of these value if you were to sell at auction or on line (eBay etc).
I hope this helps!
PS. If there's anything more I can help you with on this, please don't hesitate to ask. If not, could you very kindly rate my services (with the stars or "accept" button) as this is how I get paid by JustAnswer at no extra cost to you. We can still continue to communicate here on this thread after you do. And if you have another item you'd like to ask me about, just start a new Question and put "For Robert S....." in the subject line. Thanks, R.