The 1985, New 600EX bottom bracket (BB-6207) was a traditional design using cups, caged ball bearings and spindles. However, it did incorporate a rubber ring that sat in a groove of the cups' spindle opening and made contact with the spindle, thus sealing the bottom bracket and providing the legitmacy to use the term "sealed".

While Deore did start out as a touring group, I'm not aware of it ever having road style levers. The original Deore group used the 600EX cantilevers and levers. I suspect Miyata used the 1984/1985 New Shimano 600EX levers (BL-6207) but I can't say it with 100% confidence.