The shapes are not all perfectly round; as they are also gritty, I think they are cultured akoya pearls from WW II / Korean war era. Many of these graduated strands were sold in Japan to servicemen and others, who brought them home to their wives and sweethearts.
I have 2 such strands which I cleaned and restrung on a synthetic thread called PowerPro, using the 10# size (fine.) My restringing tutorial is stickied on the Lowly Beaders' Club page.
If you are motivated to clean them up better and restring them, they could be a lovely and sentimental strand to wear. Many here like using a very gently liquid soap (diluted in warm water) to clean pearls-- Dr. Bronner's unscented is often recommended. I've used a mild baby wash also. The pearls are best cleaned as a strand initially, but when you cut it apart prior to restringing them, wipe off any dirt that was near the drill hole, using a soft microfiber cloth, one by one. I found there was a lot of grime right around the drill hole.