Thanks for replies, so I think it's time to get a copy of Sydenham's book somehow.
I wouldn't recommend
Sydenham as your first or only book on
Roman Republican coins. While it is a useful listing and reasonably
good rarity guide, it is long out-of-date with respect to dating of the
Republican series. Perhaps a better
choice of book, which I should have mentioned previously, would be the most recent edition of volume 1 of
Roman Silver Coins (I think 1978). As its name implies it is limited to silver coins and covers the Republic to
Augustus. It contains values which are old but serve as a useful guide to relative
rarity of the coins. It is based on
Crawford dating, which has been
corrected by some recent
hoard studies but in general much more correct than
Sydenham. Alternatively, if you are also interested in
Republican bronzes, you could try
Sear,
Roman Coins and their Values either the current Volume 1 or the last single volume edition from 1988. Again, these books contain old values which can be used as a relative
rarity guide. I
hope that helps.