missiles on submarines or missiles in submarines

Context: the British political comedy Yes, Prime Minister from the 1980s (RP)

Prime Minister: How many bombs are there?

General: Four Polaris submarines, 16 missiles ? each.

There are two subtitle versions of this line: "in each" and "on each."

The Youtube caption at 1:53 says "in each".

Another source gives "on each," but it is difficult for me to show that source here.

In the adapted novel, the line reads:

‘Four Polaris submarines,’ said the General.

‘Sixteen missiles on each. Three warheads per missile.’

Ngram results: According to Ngram results, both forms appear, but which one is correct when referring to the missiles on submarines?

You would normally use "on" for a boat, but a submarine is not a typical boat, and the missiles are "in" the submarine. Both "on" and "in" are correct, with essentially no difference in meaning.

In the show, he is speaking very fast, and the preposition is reduced to 'n'. I hear it as "in".