Hypothetical WP 35S

[walter b]

@damaltor: Since the HP-30b supply will decrease as you mentioned, did you consider using the HP-17bii Silver housing and LCD instead? It may become a suitable home of your homegrown electronics IMHO, and its display is far more versatile than the one of the HP-20b/30b. Production is still running AFAIK. So you won't need bothering with housing and LCD hardware in your first step. Some new keys would do. Just food for thought.

d:-)