Thiel Owners

That will be interesting, Tom. The markings on that bypass are “PPT” which I misremembered as polystyrene rather than polypropylene.

At this point, I’m inclined to think @marqmike has FST boards rather than Lexington. 

Yes - all Lexington boards are masonite, including all the CS2.7s. I speculate that the masonite board contributes to the reported sonic advantages of the 2.7. There is a bit of mystery regarding how the 2.7 can sound so good with that huge 400uF electrolytic cap (albeit bypassed) in the midrange series feed.

Beetle -  good memory. Those 1uF bypasses had been styrene / tin foil. Some sleuthing would be required to find out if, when and why they became PP - and on which models.

Friends
I put up a picture on my systems page. I hope it shows the crossover good enough. If I need to get a better picture let me know. Thanks for helping with what you think would be the best items to upgrade on it. My speakers are 2.4's and the serial numbers are not there anymore. I don't know why though. Thanks again. 

marqmike - thanks for the photo. I'll chip in later.

@marqmike It looks like you have an earlier iteration, relative to my SEs, of the FST boards. Your coils are more tightly wound than mine were but otherwise parts quality looks equivalent save the Clarity SAs on the SE coax feeds.

If you are serious about an upgrade, I suggest at a minimum:
1) replace the sandcast resistors with Mills MRA-12s;
2) refresh the 100 uF electrolytics as those caps drift with age (best to replace those outright with metalized polypropylene film caps but 100 uF film caps are expensive and considerably larger than electrolytics to point of likely needing new boards);
3) replace all the polyester caps with polypropylene.

If it was me, I would replace everything including the printed circuit boards except, maybe, 3 of the coils. But I am a crazy person. PM me if you want specific suggestions.