Nice rifle.
Looks like a gunsmiths project. The Parker grip cap just a nice fit and touch. Parker never made any rifles AFAIK,,except for CW muskets. I'd think if it was a Parker/Remington factory job at least they'd have used a Parker grip cap screw.

The need for the bolt hold down I don't get.
Maybe the owner/builder had a bad experience with the rifle or another in the past and saw a need.
Some rifles have them like the commercial Mannlicher Shoenauer.

I like the Remington Model 30.
I picked up a 30s Express in 30-06 about a year and a half ago at a show for $250.
It sat there with no interest with a price tag of $300. The dealer thru the $250 price at me as soon as I asked to look at it.
Great condition, Lyman 48. The front ring and bbl had target scope blocks mounted. No scope. Story was the deceased owner was shooting 'long distance' (what ever that was).
I removed the bases and plugged the holes.