High yield but with an inaccurate and not available delivery system via ICBM. It would still do a lot of damage to large city targets though.
That explains why some folk insist that they saw Sputnik naked eye despite that fact that it was too small to see without optical aid. The second stage would have been a lot bigger and bright enough that the people who think they saw Sputnik actually saw that.
A tiny group at a UK school and Jodrell Bank detected the unusual signals from our first ever artificial satellite.
Sputnik's launch actually got the debts and delays of Jodrell Bank's construction completely written off as another side effect. It was in real danger of being cancelled for over budget and late. Suddenly it was relevant in a way nobody has forseen. It subsequently eavesdropped on a lot of Russian interplanetary probe telemetry famously resulting in the first pictures from Venus appearing in the British press.
Some times serendipity works in our favour.
Regards, Martin Brown