"Lasset" is one of the common names for figures sculpted by John Tassel. He collaborated with Charles Stadden/Tradition, in producing 54mm (really, 56mm), figures, and the styles are so similar, using the same tinplate bases, that the figures are often mistaken for one another, as we have done here. That is to say, they're almost interchangeable.
To give you a further idea of the comparison between Stadden and Lasset on the same subject, here are 2 side-by-side comparisons. A pair of Prussian
Jäger from the Seven Years War, Lasset (left) and Stadden (right):
and a pair of grenadiers, Stadden (left) and Lasset (right):
Generally--very generally speaking--Lassets are a little more graceful, or a little less stocky, than Staddens, in the sculpting and proportions.
Tassel also sculpted figures and sold them under Series 77 (in 77mm, hence the name). I'd have to look up the article on him in Garratt's "World Encyclopedia", to list more of his resume. As far as I know, he's still alive.
Regarding the value, Lassets go for similar prices to Staddens. For your figures, I would have looked to get them at $5 each, but $10 apiece is a good purchase price for foot figures, and $20 is a good price for a mounted figure. For finished figures, of course, the price would be expected to start higher, say, $25 for a foot figure, $50 for a mounted figure, and to increase based on the quality of the finish, and whether the painter is someone who was well-known.
As far as replacing the flag is concerned, the flags were very simple, a piece of brass rod with a piece of brass rod soldered to it, just as on the Stadden figures. Often, the base of the staff was secured to the base in a blob of solder. If this were my figure, I'd get a piece of brass rod and make the flag with thin metal foil, like lead foil or kitchen foil. I also use candy wrappers for this. The wrapper for a miniature Reese's peanut butter cup, for example, when folded into quarters, is almost exactly the right dimensions in 54mm for a Prussian infantry color. I fold the foil over the brass rod and use a little CA glue between the layers, to attach it and laminate them.
Hope that all helps, prosit!
Brad