The first bullion coin I ever bought was a Mexican 2 peso gold coin (1945, of course) that I paid a whopping $3.25 for from an ad in the August 1969 issue of CoinAGE magazine. If I could have spared an extra 70 cents, I could have bought the 2 1/2 peso instead. Today, the buying price for that 2 peso coin is around $63, while the 2 1/2 peso is fetching around $78.
LOL! Unfortunately I sold it and a few other coins a year or so later because my mom convinced me it was better to have a US savings bond. Or maybe it was Batman
If your numbers and dates are correct and accurate (no reason to suspect otherwise), then the 2 pesos has achieved an average rate of return over the 48 years of 6.37%. The 2 1/2 peso coin has achieved 6.41%. Based on: $3.25 and $3.95 cost, 48 year holding period, ending values of $63 and $78 respectively.
I still have the magazine that had the ad. The official price of gold was still $35 in those days, and the 2 peso only has about 1/20 ounce of gold, so the value of the gold in that coin at that time at the official price was only about $1.70. But the world price was a bit higher. Anyway, it's pretty interesting to go back and look at the prices of some of those coins and see how they've changed. Not only gold but lots of other coins have gone up since then, of course, but there were also a few bombs, like the 1950-D nickels and most 1955 coins that were hyped back then but haven't moved much in the nearly 50 years since.
I find it interesting as well. I've considered purchasing a set of Red Books or some other consistent guides going back every 5 or 10 years or something just to look at how things have changed over differing time periods. EDIT: Thanks for making this post.
They make great gifts as well. I recently bought my daughter Molly her first gold coin for her 9th birthday. A 2 peso.