That's interesting. I'd also like to see this ad. What was the page number?
The Lake George Youngster Class was on the minds of the folks at HMCo for quite some time during the mid-1930s. I do not know if a prototype was ever built. It would have been an open knockabout, sloop-rigged with a wish-boom, length OA 15' 0", draft 2' 6", beam 5' 3" with a sail area of 110 sq ft. Several plans for the boat, dated between September 1934 and (probably) 1938, exist at M.I.T. The Herreshoff Museum has a photo of a rigged model of it which was made in March 1937. I haven't figured out if a model of it exists, but I assume it does because its offsets were taken off and recorded in one of the offset booklets which are now in the M.I.T collection. M.I.T. also holds some technical or business records pertaining to the class.
The eighteen footer is also interesting. Might this be a reference to HMCo #1164s Louise Ann, now named Mist II and in the collection of the Herreshoff Museum? Louise Ann is variously referred to as a keel sloop of the Mount Hope or 18-24 Class. She is 23' 6" LOA, 18' 9" LWL, 6' 3" beam and has a draft of 1' 11". She was designed by N.G.H. and built for stock for the Herreshoff Manufacturing Company in March 1930. She was targeted at customers who wanted a larger and faster boat than the 12 1/2 and 16-footers. After some use for promotional service in Bristol Harbor HMCo sold her to William L. Taggart in Michigan who in 1976 donated her to the museum.