This is a Meade, adjustable mounting rail used to attach a 10” SCT OTA to a mount (e.g. to an Equatorial mount, etc.). It is in excellent condition.
The rail is cast aluminum and attaches to the 10” Meade OTA using three screws.
There is a sliding adjustment that allows the OTA to move relative to the mount – Total motion is about 1-1/2 inch. This allows the tube to be balanced on the mount. Two big thumb-screws allow the slide to be quickly clamped / released.
There are ¼-20 threaded holes, as well as through-holes, in the base that allows attaching the rail to a mount.
I am asking $45 plus shipping (probably ~$8- $12 ConUS)