Hand keys, also called straight keys, were made by T.R. McElroy from 1937 to 1943. During the war, McElroy was busy making equipment for the Signal Corps, and key production was taken over by Telegraph Apparatus Company of Chicago (McElroy was a partner in T.A.C.).

The TAC hand keys have a bulge in the lever at the contact; this distinguishes them from the McElroy keys on which the lever has the same width between the tension screw and the knob. (Note that the late McElroy hand keys and the TAC keys both used hex hardware.)

The information presented here is based on that in my 1993 McElroy book (now out of print), but has been updated to reflect more recent information. This page is a work in progress. I will add photos and descriptions of the various models from time to time.

Mac Straight Key, 1937. The "Mac Straight Key" was the first hand key McElroy offered. The 2-5/8 x 5-1/8 inch cast iron base has two mounting holes toward the front (operator's) end, so it can be screwed to an operating table, two small holes at the rear on which can be mounted an optional "Hummer" (a 1 Kc mechanical oscillator, for code practice), and a third (larger) hole at the back for the Hummer wire (this hole can be used as a mounting hole if the Hummer is not attached).
I know of two minor variations of this key: One has the two front mounting holes cast with a bevel underneath, the other variation does not.
Here is a photo of the key with the Hummer, courtesy of Lynn Burlingame, N7CFO.

The first Streamkey, 1938 - 1939. This has a somewhat flat, teardrop shaped cast brass base and (unusual for any hand key) a metal nameplate. This is probably the prettiest hand key ever made.

Toward the end of production, the plate was omitted and decals were placed on each side. The decal shown in the photo is the same as one use on the 1940 Number 500 and 600 bugs. The second decal (not shown) on the late Streamkey was unique, and read "Radio Telegraph Key, Deluxe Model, Stream-Mac." The Streamkey with decals is scarcer than those with namplates.

This key was probably intended to be made only in the Deluxe (chrome) version. However, a couple of black-wrinkle finish versions are known; these are probably very late, using up spare bases. They have no plate or decals. This "standard" version is rare.

Another view.
Decal.

Professional Model Streamkey, model 200 (1940 - 43). This has a cast iron base with a black wrinkle finish. It was available with ball bearing pivots as the BS-200, or with bronze bearing screws as the BB-200.

Late model 200. By 1942 the knurled hardware was repaced with hex hardware, and the ground pigtail from the lever was omitted, as shown here.

Pivot. Like most other manufacturers, McElroy used the pointed-cone type pivot on hand keys. But the type shown here, where the screw tip post inserts into the lever, was also used on the Streamkeys. A third type of Streamkey pivot used a single ball bearing on each side between the screw and lever; these keys were the models BB-200 and BB-300.

Cut-off key. This is a Telegraph Apparatus Company (a McElroy partnership in Chicago) key as seen by the bulge on the lever at the contact, as well as the hex hardware. It was used inside the TAC code practice oscillator. The front of the key is cut off so the lever could protrude from the front panel of the oscillator.

The plastic-based Streamkey was offered between 1940 and 1942. Early on, there were three models offered (from the July 1940 Distributor's Price List):
100, Amateur model, black plastic, cadmium plated parts, no switch (Mac's term for the circuit closer).
B200, black plastic "Professional" model, chromed parts, with switch.
G200, same "Professional" in grey plastic.

In 1941 it was offered in grey or black plastic (from an ad) as:
A-100, no switch or speed key lip
S-100, with switch and speed key lip. (This seems to have taken the place of the "model 200.") The key shown at right is a B200, or perhaps a S-100.

In 1941, the plastic key was offered as the S-100 "amateur model" (from the spring-summer 1941 catalog, and in comparison to the metal models): black plastic with switch.

A 1942 photo of the key as part of a practice set (ad, on cast iron base with the Oscillatone) shows the S-100 as a black plastic key with circuit closer and wedge lip on the connector strap.

It is not clear what the "speed key lip" means, since there is a wedge lip on the anvil contact connector strap of every one I have seen. However, since this is a plastic key, it requires another contact underneath that strap for a bug wedge. There is a cast hole in the base of every plastic key for such a contact. But I have seen only one plastic key with that lower contact installed (it is a bolt, with a strap under the base connecting to the opposite wire terminal), and that key was a cad plated Amateur model !
That's Mac, being his usual unpredictable self. (Correcting or additional information is always welcome - with references, please.)

This is an Amateur or A-100 model, with cadmium plated parts and no circuit closer.

The cast text under the lever reads "Stream Key, manufactured by T.R. McElroy, Boston Mass. USA."

The text at the back of the key reads "radio telegraph transmitting key."

Since the base is plastic, it uses a screw-head contact and a ground strip connector for the bug wedge. Oddly, this item is not often found on these streamkeys. Even more oddly, the key here is an Amateur cad plated model.