This stamp is still easy to find.
You should be able to buy a mint or a nice used copy for
20 cents.
How much is 15 cent martin Luther king stamp worth
15 cents
These are 15-cent stamps -- still good for 15 cents postage.
It will depend on the specific stamp issue. It could be minimal, worth 15 cents postage for each stamp. They may be 50 or 100 stamps to a sheet. There are some very early 15 cent stamps that could be worth many dollars each. Consult a good stamp catalog to identify the stamp and its value.
.50 cents on eBay
This stamp is Scott's number 231. A very fine used copy is worth about 10-15 cents; mint is about $8.00.
That is Scott number US 2418 It has a value of 1.30 mint and minimal 15 cent used.
Aproximately New .80 Used .40
The US Martin Luther stamp is Scott # 2065 and has a retail value of 40 cents mint and 20 cents used. However, it has a 20 cent denomination. If you have a foreign stamp you will need to specify the country. Several countries have issued Luther stamps.
That will depend a great deal on which 15 cent stamp it is. There have been stamps issued for many decades with that value. Consult a catalog and identify the specific stamp. It will also help you find the value.
This stamp is Scott number 1798. It can be purchased for about 20 cents used and 35 cents in mint condition.
That would be Scott number US 1581 or 1811. Both versions can be purchased for 15 cents mint and 15 cents in used condition.