Let's be a little more specific. The original 55, the first directional dynamic mic, was released in the 1940's. It came in 3 versions- high, medium, and low impedance. I own a 55S, the high impedance version. About 1949 (I'm not sure of the year, I'm going on memory), they switched to one version, 55SW, which had a switch for low, medium, and high impedance. In the 1950's, they reduced the size considerably, and it became known as the "small Elvis" mic. Discontinued in the 1960's, they reintroduced a retro facsimile which is still made, basically a modern mic in a retro housing.
A few useful tips- The capsule was shock mounted in foam blocks which turn to rock after a few years, and then crumble to dust. The silk screening/internal pop filter also fades, and eventually turns black. It was red in the 1940's, and changed to blue on the ones with the switch. The early ones used amphenol connectors, and changed much later to the single contact screw-on type popular in the '60's. The new ones, of course, use XLR.
So- what kind of connector does yours use, what color is the silk screen, how big is it, and does it have a 3 way switch? That should help to narrow down what you actually have, and by implication, what it's good for, and what kind of work it needs to bring it up to spec.
Last point- do a google search on "The Mic Doctor". Located in Florida, he specializes in the repair and refurbishment of old '55's. He can replace the foam blocks with modern foam, replace the silk screen with the original color, and repair housings. He also can provide amphenol connectors and cables. He does pretty good work, is fairly priced, and is reliable. Hope that helps.