Thank you both.
Perhaps in this case Isabella felt that Robert's son was best placed to administer the estate and as I suspect there was land as well as personal possessions the value may have simply been a best guess by either herself or the children at the time. My banding query was because from the indexes I have seen values seem to either be rounded up to figures under:
£50 - £450 (estate valued in whole hundreds or 50s)
£500 - £1500 (estate valued in whole hundreds)
£2000 upwards (estate valued in whole thousands)
If that makes sense. I have always wondered why the value of the estate was required to be displayed in the first place. But the suggestion regarding estate duty makes sense, maybe banding would allow ease of calculation. I did find a wikipedia link on rates of duty, which hadn't occurred to me, so thank you for that https://en.wikipedia.org/wiki/History_o ... ed_Kingdom
In any case when Isabella died she left a "personal estate under £1500" so obviously inherited at least some of her husbands money, although as I understand it under the intestacy rules at the time any land Robert had at the time of his death would have passed to his eldest son. When her will arrives I hope it may enlighten me further.