Woolworth's had their own line of mechanical pencils and matching fountain pens made by the Safford Pen Company, a division of the Parker Pen Company, Janesville, Wisconsin. Parker Pen Company was the life-work of George Safford Parker, and although he died in 1937, lamented by his wife, Martha, his family, and his friend, Frank Lloyd Wright, the company continued on successfully.
The Safford Company made a pencil for themselves much like the Woolworth model called the Fifth Ave. Not the Fifth Avenue, just the Fifth Ave. That still sounds a bit ritzy, but they are modest pencils, if you want to be tactful about it. The family desk drawer had two of these, a red Fifth Ave., and a green unmarked Woolworth version. They are tube-twist operated, with 1.1 mm lead. They have nose-drive grip on the points, but are middle twist. The red Fifth Ave. is 4 & 1/2 inches, the green Woolworth is 4 & 3/4 inches. Both have black flat tops, ball clips, and gold-ish trim.
They are mechanically the same as the Parker "Parkette," but do not carry the Parker name. Inside, they have a replaceable "lead cartridge." On both models, this is marked Woolworth. It doesn't actually do anything except store the leads and hold the eraser.
One of Parker Pens' interesting ideas was a pen which held ink pellets in a red cap on top of the pen.
The pellets became ink when dropped into the pen's water-filled barrel. These were hugely popular with soldiers during WWI. Maybe that's why the Safford pencils have a black top--they had gotten used to the general idea of a different colored top when making pens with pellets.
There's where the spare lead goes--in the slot. On the other side is printed, "When empty, throw away and replace with a. . .
Woolworth Lead Cartridge."
Fortunately, my family did not follow instructions well, so the empty cartridges are still there.