the subject of "Stencil" saxes is a convoluted one. Looking at a list like this - http://www.vintagesaxophones.com/10-STENCILS%20LIST.html it's clear that some companies ordered their stencils fro more than one manufacturer, so identifying stencil saxes is generally a case of checking for features unique to that particular manufacturer eg bevelled tone holes on Martin saxes http://www.saxontheweb.net/Resources/Stencils.html
this article gives some useful info on the differences between stencil and original brand saxes - http://www.cybersax.com/QA/Q&A_Stencil_Saxophones.html
" I don't know that ‘quality’ is the word I would pick in order to distinguish between the various stencil saxes of the 1920s. That's because the concept of cutting back on quality by using thinner metals and cutting corners by changing processes & using workers of lower skill wasn't on the radar screen back then. A stencil sax from the 1920s would be from the same body tube as the branded line, though the keywork might not include ‘extras’ like the front F, G# trill or fork Eb. I say ‘might not’ because
these stencils were made to a cost spec, and depending on the priorities of the stencilee, the instrument could have either less or more features than the branded horns of a builder. Lyon & Heally (the harp people), for instance, ordered full featured, highly decorated saxes that rivaled the top line of the stencilers. L&H stencils are almost always silver plated, and frequently have gold plated keys and gold inlaid engraving. Harwood, on the other hand, ordered mostly brass finish horns with less than full keywork and often not even pearled finger touches. The underlying horn in each case, however, is basically the same as far as tone quality and mechanical function.
Conn did not generally offer features like rolled tone holes or neck tuners on stencil saxes, but the underlying horns have the same body tube and keywork. Conn also didn't offer the straight neck C-Melody generally as a stencil. Instead you usually see the serpentine neck models in Conn stencils. With Conn though, you never say ‘never’, and I have seen one straight neck Conn C-Melody with rolled tone holes & neck tuner that did not bear the Conn name.
In general, the quality & functionality of 1920s stencil saxes follows that of the builder's branded line. That changed in the early 1930s though. After the U.S. builders had gone through their re designs in order to meet the Selmer challenge, they no longer built stencil saxes from their leading designs. Starting in the early 1930s you see stencil saxes with the body & keywork of the older designs, modified to accept a bell with two left tone holes for the low B & Bb. At first glance these saxes look like their
current branded counterparts, but they are mechanically different. Even here, I still would not use the word ‘quality’ to make a distinction, because the stencil horns were built as well as that design ever was. They just did not have the full array of current features. If you think the 1920s designs were obsolete and died out long ago, consider this: The Conn ‘Shooting Stars’ model of the 60s & 70s is a ‘Chu Berry’ with two left bell holes, and the early Selmer Bundy is a True Tone with left bell holes."
In the case of Martin, apart from the engraving or the silver plating, there's not much that they could do to simplify them any further, they're just as well built. I don't think any Martin saxes had a front F key until the late 1920's, my friend's 1926 Handcraft/The Martin certainly doesn't.
Here's a typical example of a Martin stencil - http://cafesaxophone.com/showthread.php?9637-Martin-Wurlitzer-Alto-Fully-Overhauled - still for sale at a reasonable price...
Nomenclature and clasiffication of Martins is a bit vague - my friend's family heirloom Martin only says "The Martin" on the bell, but the serial number and design put it in the "Handcraft" category... likewise all this phase 1, phase 2, phase 3 stuff is really a way of collectors to categorise saxes rather than anything that was officially done by the manufacturer - http://www.themartinstory.net/version7/models-handcraft.php
hope this is of some help