still 10x as good as the usual 8,

Internal register for a 10th for internal arithmetic, I wot.
Whether truncated or rounded in the 10th digit becomes, thus er, academic?

The hP 35: a REVOLUTION -- we stared in amazement as it proved Correct (rounding to its stated accuracy) VS a CD-6600 result to n places. Can't invent the First One again.

Anyway, the 1s-sequence is a handy quick check on some nameless box found under a bureau, with which you are about to calculate your mg/kilo-body weight of Beladonna ... or some other Interesting substance. Can't be too careful when liff is at stake.. and yer stoned.