Italian Po Levant General Issue 10c Orange Buff Variant Sg 4c

I appear to have a Italian PO Levant General Issue 10c Orange Buff variant SG 4c (all corners not altered), which even in 1969 was catalogued at £350. I wonder if there are clues that can determine if this is likely to be genuine. I think the overprint is under the postmark, which appears to be a "6" although it could be a "9" . On the back, someone has written "30" which refers to the SG number for the stamp issued for Italy, rather than the PO abroad. This is from a regular collection of Italian states, it was tucked in with other "Estero" overprints.

I have two things to ask -
Are there other things I should be looking for to determine whether this is likely to be genuine?
What is the current catalogue on this variant, and what would be a reasonable expectation for a quick sale?

Looks like a clever forgery.Letters to narrow.Look at the "R" and "O" especially..

Genuine letter set up.

You may want to see my forgery collection first .

The forgeries are shoddy with letters askew.The last stamp was in fact overprinted in 1882.
What previous collectors wrote on the album page is at times misinformation.

That is my page and I use Scott Catalog as my reference point as a general collector . Can I see your page from YOUR collection .

Auction lot no's 489 & 490
https://www.stampcircuit.com/Philat...-christoph-gärtner-gmbh-co-kg/worldwide-rarities-auction?page=19

Thank you all for your info to date. I can see that the serifs are more pronounced on the mint comparator. However, compared to the Fournier forgeries, it is more convincing. Is it worth getting this expertised, and who would be best for that?

Meanwhile, here is one from ebay currently.

Check the links for your cancel. It is in Italy.
https://goscf.com/t/52107

Wow, what a great resource. 6 and 9 are both in Italy! Thank you again perf12