Mention ‘block plane’ to the average person, and they usually think of the basic Stanley no. 110 or 220, or a competitor’s clone of the same design. These were, generally speaking, the handyman’s plane of the day, and worked just fine for occasional projects such as trimming the edge of a sticking door or window. However, those who worked with tools for a living typically used one of the more versatile models, such as the very popular no. 9-1/2 or the exceptional no. 18, both all-purpose, standard angle planes preferred for their adjustable throats and greater precision. 
Stanley missed no opportunity to make a dollar, and offering variations of their more popular planes was clearly an important factor in their strategy to dominate the industry. They offered more models and trim-lines than you could shake a unplaned stick at. Many, however, were only moderately popular and relatively shorter-lived, at least compared to the mainstay models that virtually every woodworker had in his tool box.
While the no. 9-1/2, and to a somewhat lesser extent the no. 18, enjoyed considerable popularity, Stanley also offered variations of both of these planes that, today, serve to confuse and confound new users and collectors of vintage tools. Unfortunately, Stanley’s incomprehensible numbering system did nothing to help matters, back then or now. To bring some clarity to the whole matter, here’s a brief breakdown of the variations of these two very popular models, the Stanley nos. 9-1/2 and 18.
The Stanley no. 15
no. 15 & no. 17, c. 1901-07
The no. 15 is identical to the no. 9-1/2 in every way except length – it’s approximately 7 inches long. It had one of the longest runs of all adjustable throat Stanley block planes, in production from 1876 to 1955. Given the plethora of size variations and years of production, Stanley clearly found a market for larger block planes, although the no. 15 was nowhere near as popular as its shorter brother. Subsequently, they are less common on the vintage tool market today and usually fetch higher prices.
The Stanley no. 16
no. 9-1/2 & no. 16, c.1904-09
This plane is the fraternal twin brother to the no. 9-1/2. Like the no. 9-1/2, the no. 16 was approximately 6 inches long with an iron (blade) width of 1-5/8 inches. The only difference was that its hooded lever cap, front knob, and rear wheel were tricked out in polished nickel, whereas the cap on the 9-1/2 was japanned and the knob and wheel polished brass. The no. 16 was manufactured from 1888 to 1941.
The Stanley no. 17
This plane is to the no. 15 what the no. 16 is to the no. 9-1/2. Got that? Simplified, it’s the nickeled out version of the no. 15. Since the nickel versions of Stanley planes originally cost more than their japanned counterparts, only those woodworkers with the discretionary wherewithal purchased them. I don’t see a lot of these planes out in the market, leading me to believe they were not all that popular. I guess selling bling during the 1930s depression was difficult. Just like the no. 16, the no. 17 was manufactured from 1888 to 1941.
The Stanley no. 19
no. 19 & no. 18, c. 1913-19
If there was a market for a 7 inch version of the no. 9-1/2, then logically there would be a market for a 7 inch version of the no. 18. The number 19 is just that. Sharing the same nickel plated knuckle jointed lever cap evolution as the no. 18, and the same 1-5/8 inch cutter used on all these planes, the no. 19 is identical to the no. 18 in every way except length. It was made from 1888 to 1949.
Summing it up…
The no. 15 is the 7 inch version of the no. 9-1/2
The no. 16 is the nickel version of the no. 9-1/2
The no. 17 is the nickel version of the no. 15 (and/or the 7 inch version of the no. 16)
The no. 19 is the 7 inch version of the no. 18
I suppose if you have extra big meat hooks, the larger planes might feel better in your hand. And if you like your planes tricked out, nickel-plated lever caps and hardware will help pimp your work bench. But other than length and bling, these planes are all pretty comparable to their better known counterparts, although they do tend to command higher prices since they are less common. Collectors will already know that, but for those of you looking to pick up your first or second user, hopefully this clears up the confusion.
 Standard angle refers to bed angle of 20 degrees. Sharpening the standard 25 degree bevel on the iron provides a cutting angle of 45 degrees, the same as bench planes. Low angle planes had 12 degree beds for a cutting angle of 37 degrees.
Tools shown in the photos were returned to functional condition by Virginia Toolworks using museum quality archival preservation techniques. Sharpened and tuned for use, every tool is fully tested and adjusted until perfect.