Yes it is. Once you have the length from axle to axle you can either print that image off and work out the overall length from the known length. ie, if the axle to axle length measures 4 1/2 inches and the overall length is 5 1/4 inches then it's straightforward to calculate that the overall length is the axle to axle length plus one sixth. You could even do it by measuring straight off the screen. The only variable might be the engine to tender distance and the length of the couplers since the model may differ slightly from the exact prototype dimensions.

This is how people build models based on photographs where they don't have dimensions. Take a known or guessable dimension like the height of a doorframe and scale everything off from that. In this case it's pretty easy because you have an exact dimension to work with.

This is a dimensioned drawing of a C19
http://www.ghostdepot.com/rg/rolling%20stock/locomotive/folio%20c19.gif
Now, get your calculator out. The overall length can be calculated as a percentage of the total wheelbase of loco + tender.

Well, this page has an Accucraft C19 next to an Annie with a BBT 2-8-0 drive
http://www.mylargescale.com/Community/Forums/tabid/56/aff/23/aft/123852/afv/topic/afpg/2/Default.aspx

You'll need to scroll about a third of the way down the page. Side and front shots.

@ Harold. I know that was the prototype for the 2-6-6-2 but I still think it looks a little skinny. The Serbian mallets are Baldwin built and just have a bit more heft to them.

Well, the 2-4-4-2 contains a few parts from the 2-6-6-2 but is mostly a new model and the 1:20.3 C19 is wholly new.

As Backwoods Miniatures have shown, if Bachmann wanted to go down the route of offering only variants of what they have, then they have plenty of scope just by making cosmetic changes around existing mechanisms. My guess is the current financial situation pre-dated their plans to develop both types of Mallet and the Heisler in On30 and the C19 in 1:20.3

And, the RGS had a Baldwin c42/8-18C 4-4-0

Anyone any idea how many of these and similar locomotives were built by Baldwin?

I do wonder what Backwoods Miniatures are going to do with it. They did a nice job improving the looks of the 2-6-6-2.

Doesn't the prototype have blind drivers on the 2nd and 3rd axles?
http://www.drgw.net/gallery/DRGW346/drgw_346_unknown_unknown_000 seems to be so here.

Re large scale indoors. I have seen a number of large scale exhibition layouts in Gauge 1, 1:22.5 and 1:20.3
World's End Quay (gauge 1) http://www.rmweb.co.uk/community/index.php?/blog/179/entry-393-worlds-end-quay/ was the best of them with St Jean Sur Mer 1:22.5 http://www.narrowgaugenorth.org.uk/exhibitors/past-exhibitors/93-st-jean-sur-mer a close second.  
These are large scale layouts that are not only 'indoors' but built to go in the back of a van!

The weird business with the 'same' 4-6-0 avalable in large scale, O, HO and N. i suspect they mean that they have 'a' 4-6-0 available in each scale. The magazine does not seem aimed at those who might tell one 4-6-0 from another.

Excellent. Thanks Stan That's what I couldn't see in the video but expected to be there. My preferred viewing distance for largescale is 10" (OK, I exagerate a bit ) rather than 10', since I want to trick my eye into thinking I am standing next to the real thing.

It does look nice, but both it and its larger cousin look undernourished in the boiler department, making the loco a little skinny to my eye. Another few scale inches on the boiler dia and it would have beefed up nicely. Something like this Baldwin mallet built for Serbia http://narrowmind.railfan.net/2662_Serbian.JPG (top of the page)

This would be an interesting conversion. Loses that overlong pilot. http://en.wikipedia.org/wiki/File:Swiss_Mallet_Tank.jpg

OK  I partially retract. Looked at the video again and this time I did spot the valve gear moving. Still think it needs some weathering though. I'm more inclined toward indoor and scale modelling, so it may have been the setting that disagreed with me.

Indoor large scale can be done and done well: http://www.rmweb.co.uk/community/index.php?/blog/179/entry-393-worlds-end-quay/

I was disappointed. Perhaps not so much by the loco itself as until one sees it in the flesh it's hard to judget, but certainly by the ad itself. I did wonder where the inside valve gear was as it has been there on other 1:20.3 locos like the 4-4-0 and the climax. I did spot the valve rods moving but didn't see what was making them move. Also while you can see under the boiler it looked like there was a blanking plate on top of the frames where I'd expect to be able to see down through the frames. Is there a gear train linking all the drivers? Only I thought that's what the coupling rods are for. I should add that I do not follow the 10' rule. If I wanted to view largescale models from 10' I'd work in N gauge and view from 18", thereby having more model at a lower cost.

The joy of largescale is it is literally closer to the real thing in heft and appearance, or it should be, but here the overall impression I got was that it is a smart looking 'toy' and less like the real thing than work I have seen in On30. Perhaps it was that far too clean, 'out-of-the-box' look, or the lack of a scale setting or even the salesman's voiceover, but this ad made me like the loco less!

Seconded. These two locos would open up a whole era for modelling.

I had a feeling that was so. There would be an awful lot of  faces in the UK if Bachmann brought out a Baldwin 4-6-0, as owned by 4 UK narrow gauge lines post WW1, in 1:48 scale and a lot of  faces in the US if it was any other scale.