Of the copies Michael has listed, number 3 (Arnold Books, New Zealand)
grabs my attention. It is described as "An attractive presentable copy
of the rare hand coloured version". It is also significantly cheaper
than the two copies being sold by Joseph Felcone, which have only black
and white plates.

None of the six COPAC entries for this work (http://tinyurl.com/7eecn)
says anything about hand-coloured plates, so I'm wondering whether the
coloured copy isn't in fact a copy that has been hand-coloured by one
(or more) of its owners. That is to say, perhaps the hand-coloured
version is rare because in fact there is no such version.

I found surprisingly little information online about this book. Google
turned up under a dozen pages, one of which contained a copy up for
auction, with an estimated price of GBP 200-300
(http://dukes-auctions.com/Catalogues/Pf141102/page9.htm). There's no
description of its condition, though, and it doesn't state whether the
plates are coloured or not, so it doesn't help much.

I could find nothing to confirm that there was indeed a hand-coloured
version. The next step perhaps would be to get hold of the microfilm
(Woodbridge, CT : Research Publications, Inc., 1983) and see whether
that has coloured plates.

If I there was indeed a hand-coloured version, then I would probably
have paid the extra and bought that copy. If there wasn't, and the
hand-coloured copy being offered for sale is simply a copy that someone
happens to have coloured in along the way, then the OP's copy seems
like the best deal.

There are a couple of other things which are a mystery to me. According
to some of the COPAC entries, this book was first issued in 42 parts,
and I would have expected loose copies of the parts to be knocking
around. Yet there are none.

I suppose that could be explained if they were somewhat fragile and
subject to frequent use by sporting types who literally read them to
pieces. But if that is indeed the case it would mean that Osbaldiston
had been something of a staple of 18th and early 19th century sporting
literature. And if he had in fact been such a staple then there is a
further mystery; why has his name fallen into such obscurity today? An
exact phrase search for "William Augustus Osbaldiston" turns up no
web pages at all on Google, and a search for Osbaldiston + "The British
Sportsman" turns up only a handful of pages, none of which really give
any information about the book or its author. Nor is it included in
Richard William Cox's online bibliography of British sporting
literature (http://tinyurl.com/cesrl).

Is it listed in Norah M. Titley's 1985 bibliography of British sporting
artists, perhaps? Or G. Holme's Old English Sporting Books (1924)?
Perhaps the OP can enlighten us with some information about the book
and its author.

John
http://rarebooksinjapan.com