This is just like mine except I do not have the sear block. Thank you!One sold on GB last month for $1550 with a penny start. I'd say that's a pretty good indicator of value. It had a sear block and was in nearly mint condition. No box but some original accessories.
There's another that's listed on GB now in the mid $2k price range. Looks like it's been relisted a few times.
Colt started putting sear blocks in their lowers in 89. That's also about the time they started removing the bayo lugs. You have a pretty desirable rifle since it's a pre-AWB receiver. People in some states will pay a premium because those are the only ARs they can buy.
I have a R6550 model in mint condition and I can't believe how much they sell for...when you can find one.