I always appreciate writers who gave their stories to us a long time ago and don't judge social differences. A story is current when it is published, after all. I forgive the bizarre dialogue of "Mystery In The Pirate Oak" not just because Helen Fuller Orton wrote it in 1949. She was elderly and died just six years later. Perhaps Chad and Ellie's expressions aren't so strange, considering their author was born in 1872! The history of postage stamps that she talks about, had just begun!
I learned a lot, am fond of the neighbour Grandma Hale, and the children's mother earning their living alone. There's an excellent plot: a lady returns to her childhood house, to find a silver box she left in an oak tree. My review is regretfully low, because the details didn't come together in a way that made sense. I will minimize direct discussion of plots as I explain. My Dad has a variety of childhood pictures although I imagine they were more scarce in the 1940s. But if you only had one picture of your brother and he passed away; wouldn't you go and get it as soon as possible? Perhaps write a letter to neighbours?
At the end, Grandma Hale remarks she's never seen an ocean. However we're told it is only 5 miles away. Surely there was occasion to see it, even a detour when her Grandson brought her back. The largest detail is that Chad and Ellie are pessimistic about the silver box, declaring it probably isn't there after sixty years. Any kid would jump for joy to go on a search but they are nonchalant, until they are banned from the tree. If this were re-written a bit, it would be a lot of fun in any day and age.