The existence of morasses using Silver machine in L is proved in the PhD thesis of Thomas Lloyd Richardson,  ``[Silver Machine Approach to the Constructible Universe](https://search.proquest.com/docview/302905621)''. 

See also [Silver machines](http://piology.org/img/desilver.pdf) and [Singular cardinals and analytic games](https://link.springer.com/chapter/10.1007/BFb0103111). In this last paper the author relativises the Silver machine concept to an arbitrary $L[a], a⊆ω$, and using this relativised notion he establishes a relativised version of the Jensen covering lemma.