Some Rare Italian Stamps I Cannot Identify

Hy..., as I said I Bought a collection of classic stamps..., some of them are very intriguing due to the fact that there is little or neither information related to them on the web, nor in the few catalogs I own.....I need help to identify the true value of this stamps
-20 c Volta 1927-violet..?
-15 c Caesar 1937-violet
-1929 1.75L Vitt. Em II perf 13 3/4...
-5 centessimi ,numeral inverted block o four
Thanks for your help.

Using the Michel catalogue:

Picture 1: Michel 259.

Picture 3: Michel 577

Picture 4: Michel Postage due 5 I

Thankyou very much..., can you be more specific with the value in this catalogue..., I do;nt posses it...?
What about the second stamp..., Principe Emmanuel perf 13 3/4..., it appears to be rare . but I want to figure how it worth on the catalogue ?

Welcome to the forum! You can always go to the http://stampworld.com website to find the retail price.

Peter

@melanogaster,
I really like that block of 4 with inverted figures. These 5c Postage dues are listed in Sassone in two different issues with all identical characteristics besides the colors, namely

1st issue 1870:
Cat #5 - Color 'ocra e carmino' - Nominal value 30 E for MNH single, 130 E for block of 4. For inverted figure of value, cat# 5b, a single is listed at cat value 5.500 E !

2nd issue 1890-94
Cat# 20 - Color: 'arancio e carmino' - Nominal value 1E for MNH single, 6,5E for block of 4. For inverted figure of value, cat# 20a, a single is listed at cat value 15 E.

So, probably the later issue...if not you have hit jackpot! Difficult to assist with judgement of colors based on a scan. Maybe some more experienced can help you with other markers to tell the difference between the 1st and 2nd issue.

For the 1,75L Vittorio E supposedly perf. 13 3/4...



I would check those perfs thoroughly! See from Sassone above. Could be 214, 214a, 214b - or 242....And as you know, forgeries are always a possibility.

Thanks for your replies..., the truth is that meantime I"ve made my lessons about almost all this stamps , less the 15 c Augustus 1937, violet, without egee overprint, error of color, wich I cannot find any relation along his catalog value.., can help..?

l https://www.sandafayre.com/rarestam...ystamps.html