You're very probably immune. Recovery from smallpox almost always meant life-long immunity and re-infection was basically unknown when it was common. The orthopoxviruses are known to have a lot of cross-immunity. People who get cowpox are immune to smallpox, and vice versa. The classic smallpox vaccine used widely in the 20th century was just a very mild strain of pox (genetically somewhere between smallpox and cowpox, and of uncertain origin now lost to history) which causes almost no illness in humans.

I haven't seen anything in particular about the protection resulting from a full-blown, non-attenuated infection, but as I understand it from discussions apropos another pathogen of fame lately, the rule of thumb is more comprehensive and lasting immunity from going through the disease as compared to vaccinations.

That is, I believe you ought to be in great shape compared to most of the world population.

What was it like? If it can be meaningfully described...