In last week's (this coming week in חו"ל) parsha, בהעלתך, the parsha starts out with the lighting of the menora. I would like to discuss a relatively obscure halacha which is still relevant today.
The gemara in Avoda Zara lears out from the pasuk לא תעשון אתי that you are not allowed to make figures of the sun, the moon, etc. and the כלים of the mikdash including the menora.
The Minchas Chinuch points out that the Rambam has a fundamentally different understanding of this halacha as it applies to the כלים of the mikdash then the Tur and the Shulchan Aruch. The Rambam brings this halacha in Hilchos Beis Habechira (7,10) where he discusses the halachos of מורא מקדש. The Rambam clearly understands that these dinim are not related to avoda zara. The Tur/Shulchan Aruch on the other hand brings these halachos down in hilchos avoda zara. After discussing how you can;t make the sun and the moon, they continue with these halachos.
The big question today is does this halacha apply to any 7 branch menora? The Acharonim seems to hold that the only time you violate this halacha is if the menora would be כשר in the mikdash. The acharonim discuss what about the גביעים and כפתורים on a gold menore where they are מעכב?
R' Moshe has a teshuva (יורה דעה חלק ג' סימן ל"ג) where he discusses this issue. He brings up the issue of how much oil does it need to hold, and he points out that it must hold at least enough oil for the night.
What about what to learn? Today there is a whole group of people who are building replicas of the כלי המקדש, is that permissible? Can they build a replica of the menora? R' Moshe is מיקל that for learning purposes it would be mutar. It would seem that for sure according to the Rambam it would be mutar, as there is no violation of מורא מקדש, they are trying to promote מורא מקדש.
In conclusion, the average person has nothing to fear from this din as it is very improbable that they would have a menora with 7 branches which would be כשר in the mikdash.