It's the last stage of the Revell XSL-01, and was designed by Ellwyn Angle- It's a sharp looking little kit that hasn't been re-issued since the "Space Pursuit" boxing in the late 1960's. There's some more information at:
http://www.smallspace.demon.co.uk/Space_Models/Creating_Space/EllwynAngle.htm
Box art, plans, and mission profile booklet for the XSL are at:
http://www.ninfinger.org/~sven/models/kitplans/revellh1800.html
And for the Moonship at:
http://www.ninfinger.org/~sven/models/kitplans/revellh1825.html
Hope this helps,
Andrew