Mentmore were the forerunners of today's Platignum pens. See this web site for details: 

http://hans.presto.tripod.com/scan/platignum02.html

Working from the left, the first 6 pens are early models as identified by the ball clip:

Silver snake skin patterned Mentmore Diploma SOLD

Brown marbled Mentmore Auto-Flow lever filler. Medium Mentmore Osmi Iridium 14ct nib. This nib has an unusual tip which allows the pen to write inverted as a fine grade nib. The pen is in very good condition.

Black chased Mentmore Auto-Flow SOLD

Green marbled Mentmore Auto-Flow button filler. Medium Mentmore Osmi Iridium 14ct nib. This nib has an unusual tip which allows the pen to write inverted as a fine grade nib. The pen is in good condition. There is some surface damage to the cap under the clip and extra breather holes have been drilled in it.

Black chased (fairly oxidised) Mentmore Auto-Flow button filler SOLD

Black Mentmore, no model name or number. Unusual large lever. Chrome plated clip and lever both marked with an M. Tiny fine point Mentmore 14ct nib.

The next 4 pens have the later clip, which is easily broken and thus hard to find:

Burgundy marbled Mentmore Auto-Flow lever filler. Medium Mentmore Osmi Iridium 14ct nib. This nib has an unusual tip which allows the pen to write inverted as a fine grade nib. Brassing to cap band. The pen is in very good condition.

Brown marbled Mentmore Auto-Flow lever filler. Medium Mentmore Osmi Iridium 14ct nib. Brassing to cap band. The pen is in very good condition.

Burgundy marbled Mentmore Diplomat lever filler. Medium Mentmore Osmi Iridium 14ct nib. The pen is in very good condition.

Black Mentmore Auto-Flow lever filler with rolled gold cap. Medium Mentmore Osmi Iridium 14ct nib. The pen is in excellent condition.

Burgundy marbled Mentmore Supreme lever filler. Medium Mentmore Osmi Iridium 14ct nib. The pen has a rare transparent pattern on the barrel. The pen is in good condition. This pen has a replacement clip which is not marked Mentmore but of the correct shape and design. 

The last 2 pens are later button filler models:

Black Mentmore 46 button filler with gold filled cap. The fine nib is hooded, and this pen was the Mentmore answer to the Parker 51. There is brassing to the edges of the clip. The pen is in very good condition.