The design of the menorah is laid out in the Pentateuch:
Exodus 25:31 “Then you shall make a lampstand of pure gold. The lampstand, its base and its shaft, are to be made of hammered work; its cups, its bulbs, and its flowers shall be of one piece with it. 32 Six branches shall go out from its sides; three branches of the lampstand from its one side and three branches of the lampstand from its other side. 33 Three cups shall be shaped like almond blossoms on the one branch, a bulb and a flower, and three cups shaped like almond blossoms on the other branch, a bulb and a flower—the same for six branches going out from the lampstand; 34 and on the lampstand four cups shaped like almond blossoms, its bulbs and its flowers. 35 A bulb shall be under the first pair of branches coming out of it, and a bulb under the second pair of branches coming out of it, and a bulb under the third pair of branches coming out of it, for the six branches coming out of the lampstand. 36 Their bulbs and their branches shall be of one piece with it; all of it shall be one piece of hammered work of pure gold. 37 Then you shall make its lamps seven in number; and they shall mount its lamps so as to shed light on the space in front of it. 38 Its tongs and its trays shall be of pure gold. 39 It shall be made from a talent of pure gold, with all these utensils. 40 See that you make them by the pattern for them, which was shown to you on the mountain.
Exodus 37:17 Then he made the lampstand of pure gold. He made the lampstand of hammered work, its base and its shaft; its cups, its [p]bulbs, and its flowers were of one piece with it. 18 There were six branches going out of its sides; three branches of the lampstand from the one side of it and three branches of the lampstand from the other side of it; 19 three cups shaped like almond blossoms, a bulb and a flower on one branch, and three cups shaped like almond blossoms, a bulb and a flower on the other branch—so for the six branches going out of the lampstand. 20 And on the lampstand there were four cups shaped like almond blossoms, its bulbs and its flowers; 21 and a bulb was under the first pair of branches coming out of it, and a bulb under the second pair of branches coming out of it, and a bulb under the third pair of branches coming out of it, for the six branches coming out of the lampstand. 22 Their bulbs and their branches were of one piece with it; the whole of it was a single hammered work of pure gold. 23 And he made its seven lamps with its tongs and its trays of pure gold. 24 He made it and all its utensils from a talent of pure gold.
Numbers 8:1 Then the Lord spoke to Moses, saying, 2 “Speak to Aaron and say to him, ‘When you mount the lamps, the seven lamps will provide light in the front of the lampstand.’” 3 Therefore Aaron did so; he mounted its lamps at the front of the lampstand, just as the Lord had commanded Moses. 4 Now this was the workmanship of the lampstand, hammered work of gold; from its base to its flower ornamentation it was hammered work; according to the pattern which the Lord had shown Moses, so he made the lampstand.
And yet, am I to understand that not a single menorah or image of a menorah has been recovered from prior to the 2nd century BCE. The interesting thing about this is that a menorah is something that should be pretty well preserved archeologically. We have found examples of lamps dating back over 10,000 year old. There have been thousands of lamps discovered in the region of Palestine and Egypt that are over 2,500 years old. They are indeed one of the most commonly found items, along with coins and other forms of pottery. Both clay and metal lamps are common.
But there are no menorahs.