The value of a Selmer tenor saxophone can vary depending on several factors such as its condition, the specific model, and its rarity.
Taking these factors into account, a Selmer tenor saxophone serial number 1276154 in good condition and of the sought-after "Mark VI" model could have a value between $10,000 to $20,000.
However, it is always advisable to consult with an expert or a楽器dealer to get a more accurate appraisal and to consider the current market conditions and demand.