Sure it was a potentiometer? Usually, potentiometers utilize a carbon-style track for the wiper; a few used a fine "wound wire" on a form for the wiper instead

Sure it was a potentiometer? Usually, potentiometers utilize a carbon-style track for the wiper; a few used a fine "wound wire" on a form for the wiper instead (they tend to handle higher power). If it is a potentiometer - it will have 3 connections - one to each side of the main resistance element, and a third to the movable wiper. It might be a rotary style, or it might be a linear sliding style. If it only has two connections - one to the sliding piece, and one to an end of the coil - then in that configuration it would be considered a rheostat (a potentiometer acts as a variable voltage divider, whereas a rheostat acts as a variable resistor/current limiter). If the coil is made of fairly substantial wire - then it was meant for power-controlling usage (if it is a potentiometer or a rheostat - usually a potentiometer can be used like a rheostat, but the opposite isn't possible with modifying the rheostat). It is also possible it could be a "tunable coil" - similar to what was used in early crystal radio sets; such a device is not a potentiometer or a rheostat, and shouldn't be used or confused as one.