Bullseye crank; old enough it lacks the axial adjuster bolt, new enough it has a hole for a "key" to hold the arm from walking off. At a guess, from 1984-6. Note the pinch bolt threads have been stripped or drilled and it now uses a metric bolt and separate nut. THe axial location is adjusted using an IRD "keeper" (below).

Another view, showing the arm section is rectangular.

Spline that goes inside the pinch clamp, and hole the key fits through.

IRD "keeper" — note the two ends are different diameters since one overlaps the spindle to press on the left arm.

Underside view showing right arm welded to spindle.

Newer crank with welded-in threads to use an axial bolt. This one replaces the usual Bullseye hex bolt or button screw with a countersunk Allen-head bolt.

Here's a different model, the "Safety" crank, which uses an oversize right arm that bolts on to a flanged spindle.

Bullseye inspired many other cranks — here is a BMX crank using two arms that bolt on with pinch clamps and which uses an axial bolt. The pinch bolt uses fine threads and a much larger bolt that can be much tighter.

Shimano Ultegra SL modification — Shimano supplies a knurled tool to tighten the axial bolt from 0.7 N-m to 1.5 N-m. However, there is no way to use a torque wrench on it. Here, the axial bolt is drilled and a bolt taking a 4mm Allen key is run through with LocTite&tm; and a nut on the back side. The original tool no longer fits, but this allows use of a torque wrench and means field service, installing and removing the cranks for travel, etc., no longer requres the special tool. It also means thieves don't need the special tool...

Mavic 631 "starfish" crank: