Pyro was in business for a long time. It's pretty clear that a lot of its very first sailing ship kits were indeed copied, in some cases almost literally, from wood kits made by Model Shipways (Roger B. Taney, Harriet Lane, Hildina trawler, Dispatch No. 9 tugboat) and the now long defunct Marine Models (Gertrude L. Thebaud). (I've probably missed some others.)
The little bomb ketch, however, is a good deal more recent than those. The obviously pirated ones initially appeared in the early to middle 1950s, were about 18" long, and sold for about $3.00 - about the same size and price as Revell's "first generation" of sailing ship kits (which, I think, started appearing a year or two later). That, at least, is my earliest memory of them.
The bomb ketch was part of a large range of much smaller kits, which sold initially for $1.00 each. I don't remember exactly when the first kits in that series were released, but I think it was sometime in the 1960s or maybe the 1970s. (The series included the Charles W. Morgan, the corvette Constellation, H.M.S. Bounty, a remarkably awful "English Galleon," the fishing schooner Elsie, and quite a few others. They were relatively small kits, with relatively few parts - and all of them, unless I'm mistaken, had those awful injection-molded plastic "sails." Several of them reappeared later in Life-Like and Lindberg boxes - and maybe those of other companies).
My recollections of the kits in that "$1.00 series" are vague; I bought a few of them, but frankly they were too crude and simplified to interest me much at the time. I suppose it's possible that the ones I happened to buy weren't the best in the series - which, if I remember right, eventually included at least a dozen kits.
I think I did buy the bomb ketch kit, as a matter of fact, but I fear I don't remember it well. I believe it was intended to represent a British bomb ketch of the early to mid-eighteenth century. I seem to recall giving up on it because the stern was distorted in some way, but my poor old memory may be playing me false.
It sticks in my mind that Marine Models did make a wood bomb ketch kit that looked about like the Pyro one. (Marine Models definitely made a Charles W. Morgan, and Model Shipways made an Elsie.) Whether Pyro actually based its kits on those wood ones I don't know. My recollection of the whole "dollar series" from Pyro isn't particularly favorable. All of the ones I bought were characterized by simplified, rather crude design, few parts, out-of-scale details (including laughably over-prominent "wood grain"), and, of course, those awful injection-molded "sails." I got the distinct impression that the ones I bought had been designed without any reference to plans or other genuine historical sources. I remember looking at a couple of them and concluding that, with sufficient effort, they just might be made into reasonable scale models - but in those days there were enough other, better kits on the market to keep me busy.
The pictures to which Kapudan kindly linked us pretty much confirm my memory. Notice that not only the sails but the flags are injection-molded - as are the ludicrously out-of-scale "shrouds and ratlines." The hull halves look reasonable (though the molded-in chain plates would be tough for me to accept), and the detail parts, though obviously simplified, don't look too bad. The masts do look pretty crude, and there's something decidedly odd about the shape of the one part that makes up all the decks. I seem to recall that at least one other kit in that Pyro "dollar series," the whaler, had a similar problem: the whole hull and deck appeared to have been pinched in at the stern. But for me to form a firm opinion of this kit on the basis of those photos wouldn't be fair.
If I were trying to build a model of an English bomb vessel, the first place I'd look for information would be The Bomb Ketch Granado, by Peter Goodwin, a volume in the Conway Maritime Press's Anatomy of the Ship series: http://www.anovabooks.com/book/1844860051 . There's also a good chapter on bomb vessels in the relevant volume of the Conway's History of the Ship series, The Line of Battle: The Sailing Warship 1650-1840. My guess is that examination of those books will reveal that the little Pyro kit looks generally like a mid-eighteenth-century British bomb ketch, but that making it into a genuine scale model would be almost as difficult as building from scratch. I could, however, well be mistaken. I haven't seen that kit in many years.