Examine.com has this to say about PRL-8-53:

PRL-8-53 is a synthetic supplement with potential benefits for short term memory. More evidence is needed for its effects, since all current evidence comes from a study funded by the patent holder.

The relevant study is https://link.springer.com/article/10.1007/BF00432846. Examine summarises the study thusly:

The lone study noted mild increases in memory (14%) bordering on statistical significance in high performers on a word recollection test, with higher performances in subjects over the age of 30 regardless of initial performance (108-152% increase over placebo performance) and in poor performers (87.5-105%).

Good enough for me!

On humanbenchmark.com,

My verbal memory scores are 44, 65, 93, 44, 63, 82. (77th percentile)

My sequence memory scores are 5, 6, 6, 8, 6, 10, 6, 9, 7, 6. (27th percentile)

My number memory scores are 12, 9, 11, 10, 12, 10, 11. (76th percentile)

My visual memory scores are 12, 14, 13, 14, 14, 14. (77th percentile)

I am not making particular effort to use mneumonics with these.

If I end up taking PRL-8-53, I'll check what I get on days where I take and where I don't take it and see if it seems to be improving my memory, possibly using stats. Please yell an actual experimental design at me with the analysis I should do, if you have Opinions about that. I probably won't blind the test because that sounds like effort.