I think Typoart Garamond (1955) by Herbert Thannhaeuser for Typoart (looks like an improved version of Monotype Garamond) and Garamont by Lettergieterij Amsterdam (a copy of the design by Morris Fuller Benton for ATF) should also be on a list of faux Garamonds.

What do you think of <em>Garamond Ludlow</em> (1929) by Robert Hunter Middleton?

Looks like a faux Garamond too. At least at first sight. May be nice for display, unusable for text because it is far too thin. Elegant Garamond (Bistream. now Monotype) seems to be cloned from Ludlow Garamond.

Let’s also do a list of True Garamonds:

Stempel Garamond (Stempel, 1925)
clones of Stempel Garamond:
Original Garamond (Bitstream)
CG Garamond (Compugraphic, Agfa Compugraphic, now Monotype)

Sabon (Jan Tschichold, Stempel/Linotype/Monotype 1967)
clones of Sabon:
Sabon (Ascender, now Monotype)
Classical Garamond (Bitstream, now Monotype)

Berthold Garamond (Günter Gerhard Lange, Berthold 1972)
clones of Berthold Garamond:
URW Garamond (URW)

Adobe Garamond (Robert Slimbach, Adobe, 1989)

Sabon Next (Jean François Porchez, Linotype, 2002)

Garamond Premier (Robert Slimbach, Adobe, 2005)

what else?

Albert: an old Bitstream catalogue equates Elegant Garamond with Granjon (Linotype), which I think is usually counted as a true Garamond, despite its name.

The Ludlow Garamond was 'revised & digitised' by Jill pichotta for Font Bureau

http://www.fontbureau.com/fonts/serif/GaramondFB/

¶ The Ludlow version displays too much contrast so it can't be French Renaissance.

¶ Read the description of the updated Ludlow Garamond:

Condé Nast commissioned the FB version of this popular oldstyle for Traveler magazine. Douglas Crawford McMurtrie, type historian, and type designer Robert Hunter Middleton collaborated at Ludlow in 1929 to design a light oldstyle roman and italic, then released them light-heartedly under the name of “Garamond”. Jill Pichotta revised and digitized them both, adding additional weights with italics to the series; FB 1992–2000.

So if you have one in hand, how do you tell if it is 'fake' or 'true'? If you don't have a list? If it isn't on a list?

Well, compare it to the ones that are on the list. That would yield more accurate results than trying to put the distinction into words.

¶ Any thoughts on the typeface Laurentian based on Garamond.

Looking it up, it apparently was based partly on Garamond and (to a lesser extent) partly on Caslon; it was a custom typeface created for the Canadian publication Maclean's magazine. (Maclean's is Canada's major weekly news magazine, competing against TIME and Newsweek.)

Looking at the specimen on MyFonts, it didn't seem to have the distinctive "Garamond" feel I associate with the Jannon-based "fake" Garamonds, however, I wouldn't say that this necessarily brings it closer to the "real" Garamonds; it could, but I don't feel qualified to judge that.

What about George Abrams’s Augereau?

What about George Abrams’s Augereau?

¶ Abrams payed a tribute to the Garamond. Nice typeface and not far away from Slimbach.

• Peignot Garamond (1926) by Georges Peignot

Is this what you mean?

Please notice the Le in the name of the typeface, and the terminal t, not d (that’s how Georges and Jacques Peignot spelled it), and the dates, 1914–23. The source: Charles Peignot. « Les Peignot : Georges, Charles ». Communication & langages, Volume 59, Issue 59. Paris : Armand Colin, 1984, p. 78.

Please notice the Le in the name of the typeface, and the terminal t, not d (that’s how Georges and Jacques Peignot spelled it), and the dates, 1914–23. The source: Charles Peignot. « Les Peignot : Georges, Charles ». Communication & langages, Volume 59, Issue 59. Paris : Armand Colin, 1984, p. 78.

¶ It's the old controversy between the Latin nickname and the real name: Garamondus (Garamond) versus Garamont. Goudy also called his version Garamont.

¶ After using the name of Garamont's teacher, Augereau, any thoughts on the very rare hot metal Linotype Estienne by George William Jones?

¶ I wonder why there are no Le Bé or Haultin typefaces?

¶ How would you define and classify the Garamond-oriented typefaces?

Augereau
Laurentian
Minion

¶ The Ludlow version displays too much contrast so it can't be French Renaissance.

Dear Stefan Miklos, why should high contrast not be a feature of French Renaissance / Garalde? The display sizes of Garamond and other typefaces from that era had a higher stroke contrast than the smaller sizes. I think we should not mix up high contrast as in French Renaissance display sizes with thin(ner) hairlines as in Bodoni / Didonic typefaces. Due to the pointed-nib stroke contrast, which is typical for Bodoni / Didonic typefaces, the horizontal curves in lower case characters have far less weight, resulting in more thin hairlines as in French Renaissance / Garalde. From this point of view, in Bodoni / Didonic typefaces contrast is not necessarily higher, it is only more apparent in horizontal curves. In short: we should not mix up between size of contrast and kind of contrast.
Back to high contrast: What happened is that with the introduction of large drawings for the pantographic engraving machines in the 19th centuries prints of large type sizes were used for rendering rather prints with small sizes. Taking in account that the Ludlow machines were originally conceived and most used for casting headline sizes, it seems that using large sizes of metal type to create drawings for the pantographic matrix engraver was a good idea at Ludlow. Using these designs for digitizations of typefaces that are also intended for use in text sizes seems like less brilliant idea.
Unfortunately it took a rather long time before the drawing offices and typeface designers became fully aware of the consequences of downscaling large sizes for small sizes. Also the phototypesetting era and digital typesetting preceding PostScript and TrueType, not much attention was paid to this. The introduction of optical sizes, followed by the optical axe in Variable Fonts are the first wide-scale attempts to solve the problem of scaling.