Technical SBC Cylinder Head Casting Mark ID

I've done some searching and haven't been able to find this casting mark on any of the SBC Head ID charts. Seller hasn't responded with any head numbers, so I'm turning to the HAMB encyclopedia for help.

Seller says engine is a 327, but the ad has photos of two different block casting numbers, one for a 283 and the other for a 302/327/350.

 

At first glance it looks like an "L" shape (on it's side) - but if you blow it up, it appears to be an upside down "T". If it is, that would make it a 3998991 - 72 to 73 307/350 75cc chambers.

 

I believe you are right. Thanks!