It's unlikely to appear in Bauer's publications because he coined and used the Keller metaphor. It is much more likely to appear in later publications that trie

It's unlikely to appear in Bauer's publications because he coined and used the Keller metaphor. It is much more likely to appear in later publications that tried to translate stack but at the same time wanted to pay tribute to Bauer, hence the usage of both Keller and Stapel.