I recently acquired a ‘Pre Must’ Cartier Tank Louis with reference no. 15705 that I believe dates back to the early 1970s. It was made during the time when the Cartier boutiques were operated separately in New York, Paris and London. I would love to know more about this watch so if there are others out there who own this piece, please share some photos and information on when and where it was purchased! I am no expert so all the information that is writen in this post have been compiled after hours of research. This Pre Must Tank has a manual wind Cartier 78X movement (ETA 2512 base). Later manual wind Must models from the late 1970s use the Cartier 78-1 movement (ETA 2512-1 base) instead. Its size is approximately 30mm height by 23mm width excluding the crown, making it the model for men at that time. This post only includes pictures of pieces with screw on case backs and punched logo, which is said to be from the New York boutique. Pieces with snap-on case backs have been excluded as they seem to be far more common. After hours of scouring the internet, these are the information I could find. From the internet: - Ref. 15705 Tank Louis is from the New York boutique - Due to the use of a patented screw-on case back back then in the early 1970s, this particular reference could not be faked. - Gold plated over base metal (likely brass) From observations: - White dial with SWISS under VI - Elongated blue carbochon crown - Earlier serial numbers seem to have a thicker crown - Unlike the Must series, there is no hidden Cartier mark on VII, or on X like other modern pieces - The first number 4 on the case back seem to indicate that this is for men. The smaller sized pieces with the same case back markings start with a 1 - The original buckle for the strap has a double C logo that looks very similar to Chanel Pictures of this ref. 15705 with smaller serial numbers seem to also have a long 10 digit reference number of some sort engraved on the inner side of the case. I only own 1 of the watches below. The other pictures were taken off of the internet. 1. This is the copy I own Serial number on case back: 4 00476 Innerside of case back: 15705 7808600867 Item has just been shipped by the seller and I do not have it with me at the moment. Pictures that the seller provided were quite blurry. Will get it restored. 2. Not mine Serial number on case back: 4 01005 Innerside of case back: 15705 7808600699 3. Not mine Serial number on case back: 4 02210 Innerside of case back: ????? 4. Not mine Serial number on case back: 4 03748 Innerside of case back: 15705 5. Not mine Serial number on case back: 4 04??? Innerside of case back: 15705 6. Not mine Serial number on case back: 4 05101 Innerside of case back: ????? 7. Not mine Serial number on case back: 4 05217 Innerside of case back: ????? 8. Not mine Serial number on case back: 4 05945 Innerside of case back: ????? 9. Not mine Serial number on case back: 4 09730 Innerside of case back: 15705 10. Not mine Serial number on case back: 4 0???? Innerside of case back: ????? These are all the pictures I could find on the internet. It seems quite elusive but I may be wrong. Please let me know! This is the strap buckle for this model. It was more square and had interlocking Cs. Once again, I am no expert and the information written in this post stands to be corrected! Regards, Hensley