I suppose I am old enough to remember the first (to me) Christmas scented smoke fluids, sold by LVTS - Lehigh Valley Train Service. There were at least 2-3 different Christmas scents, as well as other scents, coal, hickory, etc. Back in the late 1990s, liquid smoke fluid was new to me, and after purchasing a bottle of their stuff at a train shop, and loving the smell of Christmas, I eventually needed more and had noted the label on the bottle denoted the maker of the liquid was based out of Emmaus, PA.
I ended up calling and stopping over and buying case of the Christmas scented stuff as my in-laws lived in Emmaus and we would see them regularly. I recall he had a small repair shop in the back of town near the old Reading Lines, maybe some trains for sale.
MTH had used LVTS...and so it was/is good stuff for making smoke in toy trains, if you like that effect. At some point, the little plastic containers that MTH included with engines changed to MTH Smoke fluid, and don't know if they used the same formula. I still have the empty bottles of the LVTS at various places in my basement, which have a residue in them, and every now and again open them up for a sniff of Christmas, ahh - good stuff 
...will search my basement for possible empty, or partially full bottles...likely not more than a drop or two left.