If it's one of the built-in layouts, those are all core2.
If it's a custom layout, go to advanced customization/your layers. Every journal style is made up of multiple "layers," and all of the layers that make up the currently activated style are highlighted in a different color.
So, find the "layout" layer for your current theme and see what layer it says it's a "child" of. Core2 layouts say "Child of layer 550: Dreamwidth S2 Core, v2". So, I think core1 layouts would say the same thing except "v1". (I haven't gone to check the actual string it uses.)
no subject
If it's one of the built-in layouts, those are all core2.
If it's a custom layout, go to advanced customization/your layers. Every journal style is made up of multiple "layers," and all of the layers that make up the currently activated style are highlighted in a different color.
So, find the "layout" layer for your current theme and see what layer it says it's a "child" of. Core2 layouts say "Child of layer 550: Dreamwidth S2 Core, v2". So, I think core1 layouts would say the same thing except "v1". (I haven't gone to check the actual string it uses.)