Tom, many years ago I worked in a pattern shop. As you stated we often made a wood pattern ,then sent it out to the
place that made the aluminum "match plate". When we got it all back we then scraped off small pieces of flashing and
such before sending it to foundry. Sometimes after trying it out, the mfg. would tell us there was too much metal to quickly machine off in
a stated area. Then they sent it back to us to alter match plate. Sometimes an area of 15 inches ,or more, and 1/8 inch
high had to go. We would chisel file and scrape and curse the shrink rule.