I've bought two pairs over the past 2 years for the 400/4 and the CB250RSA. I first looked at them from the guy that sells them in the south of England, he's a TEC rep. They looked OK although some of the chrome on the springs is as you say, a bit ropey but not on all of them and the shock body is fine. I order a set from TEC themselves and the set sent were fine. The set I bought for the RSA I bought from Kempton, the chrome wasn't good on the springs on the first set offered and I rummaged through the others and found a really nice set.
To be fair to TEC they do provide excellent after sales and are very helpful if you call them. The shocks are Australian made apparently to a Koni design? For me they are a bargain, they work well and are not the usual ugly looking poor quality Chinese pogo sticks.