Good Challenge
LM!
Thanks for the PM
I can't find anything that matches the spacing, shape and angles of the fins! Most seem to be too close, longer or steeply angled or are a Skunk Works product
You said it was a project, but wasn't from Lockheed, however, you didn't say it
was American, so I'm wondering if it could be one of the concepts put forward in response to the MOD's "High Agility, Low Observability" programme of the nineties. They did consider this would be a Tornado replacement and initiated HALO after the demise of the American A-12 program. I looked at that, but it had wide fins and was too curvy (yours looks faceted to me). Maybe this will elicit a few more more clues for the others to work on
Got to go now so can't dig any deeper, back Monday. Have a good weekend and keep up the good work!