Vintage Women's Milus Bracelet/ Watch

I bought this from a lady today and..she said that it had belonged to her mom. She said her father gave it to her mother in 1951..it looks great, works great and says 18k on the back..she said she didn't know if it was gold or gold plated..she said it meant a lot to her and that if I decided I didn't want it, she would buy it back from me..can't go wrong with that deal..I am just wondering if it is real gold..I couldn't find one like this anywhere..on the back by the 18k, there is a mint mark that is in the shape of a guitar pick, maybe a heart, with a silhouette of a woman looking sideways..any information would be great, thank you!