Every day's a school day! Interesting article below about Fisk coffins: form fitting, airtight and made from cast iron (you may need a paywall remover).

@chriswoodyard.bsky.social explores these more in her excellent book, A Is For Arsenic, An ABC of Victorian Death.

https://cdispatch.com/news/caskets-likely-from-the-1800s-found-unmarked-in-friendship-cemetery