Earl is just another name for Count; an Earl's wife is in fact a Countess, as is a female holding the title in her own right (sole heir, of oldest of females with no male heirs.).
Viscount has equivalents in some but not all european systems of nobility; currently the most common use I've encountered (outside the SCA) is that of the Courtesy Title of the heirs to a County in Britain. I've read that it was common enough in France, and hence why it appears at all in Russia...
Duke/Herzog/Vevoda/Dux is fairly common
Marquis/Margraf/Marchio/Markize is likewise common
Count/Comes/Contes/Graf is nearly ubiquitous in former Roman dependencies
Baron is less common as a title in its own, but is better known and more often used in science fiction.
Knighthood is not a rank of nobility in some systems, but is either the lowest rank of noble or highest rank of non-noble
In pre traveller Sci Fi, of which I've read a bunch, but by no means an exhaustive or even vast sample, I have encountered only a few ranks of nobility and royalty:
Emperor
King
Prince
Duke
Count
Baron
Demi-baron (Dune)
Lord
If we were to revise to include the various grades-common, we'd wind up with something akin to:
Emperor
King
Arch Duke
Prince
Grand Duke
Duke (Royal)
Duke (Noble)
Marquis
Count
Viscount
Baron
Baronet or Signeur
Knight
Lord
That Marc (uncharacteristically) restricted to 5 the player titles (instead of 6) is an oddity in itself, ESPECIALLY given the 3 additional ranks mentioned in the back of Bk 3...
BGG: Unless you purchased it VERY early on, it may not have been 1st printing... since 7th printing is different from first, and is still "1st Edition"
There was a discussion on one of the traveller boards (I think it was here, I'm searching for it) that references the appearance and disappearances of various bits in the so called "first edition".
And, while "Second Ed" is 1981, Supp3 gets revised along with it... I've seen/owned two different printings, and they are not identical in content. But both of them support a "Largish" imperium.
Hans: Which printing LBB's are you using?