This may not help very much, but there are records that a 16-size, 21-jewel, open-face Invar watch serial number 191790, in a gold-filled case, was serviced in Calgary, Alberta, Canada several times during the 1930s.
I've seen several other examples offered for sale over the years, either by mail order dealers or on the internet. They were only memorable because, as Doug pointed out, the name is linked to a material used in trying to reduce the effects of temperature (and perhaps magnetism) on timepieces.
So, by all indications your watch sounds like a 'private label,' or 'contract,' watch from a relatively small retailer. Just about all the watch companies, including the Swiss firms, would mark both the watch movements and/or the dials in just about any manner for any customer who wished to pay for the service. I don't have any exact references for the costs, but I've heard (read?) that, for some companies, if five or more watches were ordered, there was no charge for marking the movements. Special dials were said to cost 25 or 50 cents each. Some watch manufacturers were more liberal.
