Diamondback history from Wikipedia:

Diamondback Bicycles was founded as a BMX brand in 1977 by Western States Imports in Newbury Park, California, which sold bikes under the Centurion (bicycle) brand. Early in its history, the brand name was "Diamond Back" and over time this changed to "DiamondBack" and then to "Diamondback." Beginning in 1990, Western States Imports started selling its mountain bikes and road bicycles under the Diamondback name as well. Since 1979, many riders have successfully competed under the sponsorship of Diamondback, which began with BMX and expanded to Mountain Bikes with the creation of Diamondback Racing (DBR) in 1993.

In 1999, Diamondback Bicycles was purchased by the Derby Cycle Corporation, which also owned the Raleigh Bicycle Company, and merged Raleigh and Diamondback together. In 2001, Derby Cycle Corporation sold Raleigh and Diamondback. In August 2019 Accell Group sold Diamondback to Regent, L.P

I sold a lot of their bikes back in the "Raleigh era," and still ride one of them. I always had good responses whenever I needed to contact them about any issue.

Try placing an inquiry with the company via the "Contact Us" option on the diamondback.com web page. You might also contact Derby Cycle who still make the Euro Raleigh.